Electrochemical methods, devices, and structures

ABSTRACT

The present invention provides devices and structures and methods of use thereof in electrochemical actuation. This invention provides electrochemical actuators, which are based, inter-alia, on an electric field-driven intercalation or alloying of high-modulus inorganic compounds, which can produce large and reversible volume changes, providing high actuation energy density, high actuation authority and large free strain.

CROSS REFERENCE TO RELATED APPLICATIONS

This invention claims priority from U.S. Provisional Application Ser.No. 60/578,855, filed Jun. 14, 2004 and U.S. Provisional ApplicationSer. No. 60/621,051, filed Oct. 25, 2004, which are hereby incorporatedin their entirety.

FIELD OF THE INVENTION

This invention provides devices and structures and methods of usethereof in electrochemical actuation. This invention provideselectrochemical actuators, which are based, inter-alia, on an electricfield-driven intercalation or alloying of high-modulus inorganiccompounds, which can produce large and reversible volume changes,providing high actuation energy density, high actuation authority andlarge free strain.

BACKGROUND OF THE INVENTION

Actuation is essentially a mechanism whereby a device is turned on oroff, or is adjusted or moved by converting various types of energiessuch as electric energy or chemical energy into mechanical energy.Mechanical energy can be stored as elastic energy in a material or adevice, or can be used to produce useful mechanical work, which isdefined as the product of stress and strain. Thus a useful measure ofthe potential for actuation of a given material or device is theactuation energy density (energy per unit volume). The actuation energydensity is also useful for distinguishing the capabilities of differentactuation methods. The specific (or gravimetric) energy is readilyobtained from the energy density knowing the density of the materials ordevice. While the “free strain,” or strain produced under zero or nearlyzero stress conditions, is sometimes used to characterize actuators oractuation materials, this is an inadequate measure of actuationcapability since no mechanical work is done. Thus, the capability formechanical work can only be known when the strain produced against aknown mechanical stress, or the stress produced under known conditionsof strain, are known.

Different types of actuators are categorized by the manner in whichenergy is converted. For instance, electrostatic actuators convertelectrostatic forces into mechanical forces. Piezoelectric actuators usepiezoelectric material to generate kinematic energy. Electromagneticactuators convert electromagnetic forces into kinematic energy using amagnet and coil windings.

Actuation, in theory, would find application in the production ofadaptive and morphing structures, though practically such an applicationhas not produced ideal results. Piezoelectric actuation provides highbandwidth and actuation authority but low strain (much less than 1%typically), and requires high actuation voltages. Shape memory alloys(SMAs), magnetostrictors, and the newly developed ferromagneticshape-memory alloys (FSMAs) are capable of larger strain but produceslower responses, limiting their applicability. Actuation mechanismsthat are based on field-induced domain motion (piezos, FSMAs) also tendto have low blocked stress. All the above actuation methods are based onthe use of active materials of high density (lead-based oxides, metalalloys), which negatively impacts weight-based figures of merit. Thusthere is currently a great need for a technology capable of providinghigh actuation energy density, high actuation authority (stress), largefree strain, and useful bandwidth.

Certain methods of actuation using electrochemistry have previously beendescribed. For example, K. Oguro, H. Takenaka and Y. Kawami (U.S. Pat.No. 5,268,082) have described using surface electrodes to create ionmotion under applied electric field across an ion-exchange membraneresulting in deformation of the membrane. W. Lu, B. R. Mattes and A. G.Fadeev (U.S. Patent Application No. 2002/0177039) have described usingionic liquid electrolytes in conjugated polymers to obtain dimensionalchange. R. H. Baughman, C. Cui, J. Su, Z. Iqbal, and A. Zhakidov (U.S.Pat. No. 6,555,945) have used double-layer charging of high surface areamaterials to provide for mechanical actuation. D. A. Hopkins, Jr. (U.S.Pat. No. 5,671,905) has described an actuator device in whichelectrochemically generated gas pressure is used to provide formechanical motion. H. Bauer, F. Derisavi-Fard, U. Eckoldt, R. Gerhrmannand D. Kickel (U.S. Pat. No. 5,567,284) have similarly usedelectrochemically-produced gas pressure in a pneumatic actuation device.G. M. Spinks, G. G. Wallace, L. S. Fifield, L. R. Dalton, A. Mazzoldi,D. De Rossi, I. I. Khayrullin, and R. H. Baughman (Advanced Materials,2002, 14, No. 23, pp. 1728-1732) have described a pneumatic mechanismusing carbon nanotubes in which aqueous electrochemistry is used togenerate gas within a confined space allowing for mechanical motion. Ineach of these non-faradaic approaches, the load-bearing actuationmaterials are inherently a gaseous or liquid phase and may be expectedto have low elastic modulus and consequently low actuation energydensity and actuation stress, compared to the approach of the presentinvention.

With respect to solid-state electrochemistry, it is well-known to thoseskilled in the art of solid state intercalation compounds, for instance,those working in the battery field, that certain compounds undergoexpansion or contraction as their chemical composition iselectrochemically altered by ion insertion or removal (faradaicprocesses). K. Takada and S. Kondo (Solid State Ionics, Vol. 53-56, pp.339-342, 1992, and Japanese Patent Application 02248181) have furtherdemonstrated free strain in consolidated solid compounds undergoingelectrochemically induced composition change. They reported about 0.1%free strain using Ag_(x)V₂O₅ as a Ag intercalating compound, which is alevel of strain comparable to that reached by many commercialpiezoelectric materials (e.g., those based on lead-zirconium-titanate(PZT)). However, no mechanical load was provided and so mechanical workwas not demonstrated despite the observation of displacement. G. Gu, M.Schmid, P.-W. Chiu, A. Minett, J. Fraysse, G.-T. Kim, S. Roth, M. Kolov,E. Munoz and R. H. Baughmann (Nature Materials, Vol. 2, pp. 316-319)have used mattes of V₂O₅ nanofibres for actuation using aqueouselectrochemistry. In this instance, they reported strain under unloadedconditions of up 0.21%, and the production of stress under nominallyzero-strain conditions of up to 5.9 MPa, although whether the processused to generate the stress was faradaic or non-faradaic was not known.

SUMMARY OF THE INVENTION

The invention provides, in one embodiment, an electrochemical actuator,comprising an negative electrode, a positive electrode and anintercalating species, wherein the electrochemical actuator is subjectedto an applied voltage, whereby application of the voltage or cessationthereof induces intercalation of the intercalating species in theactuator, resulting in a volumetric or dimensional change of theactuator under conditions of mechanical constraint or loading resultingin the production of useful mechanical energy.

In another embodiment, the invention provides a Multilayer StackedElectrochemical Actuator, comprising two or more negative electrodelayers, two or more positive electrode layers, and an intercalatingspecies, wherein the Multilayer Stacked Electrochemical Actuator issubjected to an applied voltage, whereby application of the voltage orcessation thereof induces intercalation of the intercalating species inthe actuator, resulting in a volumetric change of the actuator resultingin the production of useful mechanical energy.

In another embodiment, the invention provides a RotationalElectrochemical Actuator, comprising rolled layers of an negativeelectrode, a positive electrode and an intercalating species, whereinthe rolled layers assume a laminate configuration, and wherein theRotational Electrochemical Actuator is subjected to an applied voltage,whereby application of the voltage produces intercalation of theintercalating species in the actuator, resulting in a volumetric ordimensional change of the actuator such that the rolled laminateconfiguration winds or unwinds, and torque is produced.

In one embodiment, following when the rolled laminate configurationwinds or unwinds, rotary motion is produced. In one embodiment, therotary motion ranges from 1-360°. In another embodiment, the rotarymotion produces 1 or more rotations. In another embodiment, the 1 ormore rotations are complete or incomplete. In another embodiment, therotation is in a clockwise direction or counter clockwise direction, ora combination thereof.

In another embodiment, the invention provides a Continuous FiberElectrochemical Actuator, comprising a fibrous electrode, a counterelectrode and an intercalating species wherein the Continuous FiberElectrochemical Actuator is subjected to an applied voltage, wherebyapplication of the voltage or its cessation induces intercalation of theintercalating species in the actuator, resulting in a volumetric ordimensional change of the actuator, such that said fibrous negativeelectrode undergoes elongation and produces useful mechanical work. Inone embodiment, the volumetric or dimensional change is induced intension as well as in compression.

In another embodiment, the Continuous Fiber Electrochemical Actuator iscomprised of multiple coated fibers, which are utilized to form a fibercomposite. In another embodiment, the composite further comprises amatrix, which, in another embodiment, is a polymer. In anotherembodiment, the composite of the Continuous Fiber ElectrochemicalActuator comprises fiber ends, which are uncoated. In anotherembodiment, the uncoated ends of the fibers enable electricalconnections to be applied to the ends of the fibers.

In another embodiment, the Continuous Fiber Electrochemical Actuatorcomprises multiple layers, which, in another embodiment are assembled inparallel or in perpendicular orientation. In another embodiment, theperpendicular orientation allows positive and negative shearingactuation of the actuator, which, in another embodiment, producestorque, or, in another embodiment, produces rotation. In anotherembodiment, the perpendicular orientation allows for charge transferbetween layers when low voltage is applied.

In one embodiment of the invention, intercalation of the species in anactuator of this invention can occur upon both application of thevoltage and cessation thereof. In another embodiment, the extent ofvolume change is controlled by controlling the amount of current flowinto or out of the actuator. In another embodiment, the volumetric ordimensional change is in the negative electrode or positive electrode ora combination thereof. In another embodiment, the volumetric ordimensional change is reversible. In another embodiment, theintercalation produces high strain against a substantial mechanicalload. In another embodiment, the negative electrode, or in anotherembodiment, the positive electrode, serves as a donor or acceptor orcombination thereof of the intercalating species.

In another embodiment, an electrode of an actuator of this invention isinitially enriched in, and may serve as a source for, the intercalatingspecies. In another embodiment, a negative electrode of an actuator ofthis invention may serve as a source for the intercalating species. Inanother embodiment, a positive electrode of an actuator of thisinvention may serve as a source for the intercalating species.

In another embodiment, the electrode comprises a high elastic moduluscompound. In another embodiment, an electrode comprises an iontransition metal oxide. In another embodiment, the ion in said iontransition metal oxide is a proton or an alkali metal or an alkalineearth metal. In another embodiment, the alkali metal is lithium. Inanother embodiment, an electrode comprises: LiCoO₂, LiFePO₄, LiNiO₂,LiMn₂O₄, LiMnO₂, LiMnPO₄, Li₄Ti₅O₁₂, and their modified compositions andsolid solutions. In another embodiment, an electrode comprises: an oxidecompound comprising one or more of titanium oxide, vanadium oxide, tinoxide, antimony oxide, cobalt oxide, nickel oxide or iron oxide. Inanother embodiment an electrode comprises TiSi₂, MoSi₂, WSi₂, and theirmodified compositions and solid solutions. In another embodiment anelectrode comprises a metal or intermetallic compound. In anotherembodiment an electrode is lithium or a lithium-metal alloy, which maybe crystalline, nanocrystalline, or amorphous. In another embodiment thenegative electrode is one or more of aluminum, silver, gold, boron,bismuth, gallium, germanium, indium, lead, antimony, silicon, or tin. Inanother embodiment, an electrode is carbon in the form of graphite, acarbon fiber structure, a glassy carbon structure, a highly orientedpyrolytic graphite, a disordered carbon structure or a combinationthereof. In another embodiment, the intercalating species is an ion. Inanother embodiment, a proton or an alkali metal or an alkaline earthmetal.

In another embodiment, the negative electrode or positive electrodecompound undergoes anisotropic expansion or contraction uponintercalation.

In another embodiment, the compound is textured or oriented in theelectrodes of the actuator resulting in anisotropic expansion orcontraction. In another embodiment, the compound is oriented in theelectrodes of the actuator to increase the dimensional change in theprimary actuation direction of the actuator upon intercalation oralloying. In another embodiment, the negative or positive electrodecompound undergoes a phase change upon intercalation orde-intercalation. In another embodiment, the negative or positiveelectrode material is in the form of a single crystal, polycrystal, orfine powder. In another embodiment the fine powder is of anisometricparticle shape. In another embodiment the fine powder has a platelet orrod-like morphology. In another embodiment the smallest dimension of thepowder particles is on average less than about 100 micrometers.

In another embodiment, one or more electrodes of the actuator comprise aporous sintered aggregate of the negative or positive electrodecompound. In another embodiment, the porous sintered aggregate is acomposite comprising also a conductive additive or sintering aid. Inanother embodiment the sintered aggregate has crystallites of anelectrode compound that share a common orientation or texture of theircrystal axes, which in one embodiment is uni-axial, and in anotherembodiment is biaxial.

In another embodiment, one or more electrodes of the actuator comprise acomposite containing a powder of the negative or positive electrodecompound, an organic or inorganic binder, and optionally a conductiveadditive. In one embodiment the binder is a polymer, and the conductiveadditive is carbon. In another embodiment, the volume percentage of theelectrode compound in the electrode is at least 45%. In anotherembodiment the particles of the compound are anisometric in shape, andhave a preferred common orientation. In another embodiment, theparticles of the compound are crystalline, and have a preferred commonorientation or texture of their crystal axes, which in one embodiment isuni-axial, and in another embodiment is biaxial. In another embodiment,the composite electrode is fabricated by mixing its constituents in anaqueous or inorganic solvent, coating and drying the mixture, andpressing or calendaring the coating.

In another embodiment, an actuator of this invention further comprises acurrent collector, which, in another embodiment, comprises a conductivematerial. In another embodiment, an actuator of this invention furthercomprises a separator, which in one embodiment is porous, or in anotherembodiment, is rigid. In one embodiment, the porous separator comprisesa microporous polymer. In another embodiment, the porous separatorcomprises a porous electronically insulating ceramic material, which inanother embodiment is alumina, an aluminosilicate, cordierite, or asilicate glass.

In another embodiment, an actuator of this invention further comprisesan electrolyte. In one embodiment, the electrolyte is a solidelectrolyte, which in one embodiment is a polymer, and in anotherembodiment an inorganic crystal or glass. In another embodiment, theelectrolyte is a liquid or gel electrolyte. In another embodiment, anactuator of this invention further comprises an external packaginglayer, which may be, in one embodiment, an electrochemically-insulatinglayer, or, in another embodiment, a protective layer or, in anotherembodiment, a combination thereof.

In another embodiment, this invention provides an actuator device inwhich an electrochemical actuator of this invention is further used inan actuator structure that provides for stress amplification (straindeamplification) or stress deamplification (strain amplification).

In another embodiment, an electrochemically-actuated strain deamplifying(stress amplifying) actuator device having a woven structure isprovided.

In another embodiment, an electrochemically-actuated strain amplifying(stress deamplifying) lever actuator is provided.

In another embodiment, this invention provides a structure or apparatuscomprising an actuator of this invention. In one embodiment, thestructure or apparatus is adaptive. In another embodiment, the actuatoris used as an element to apply stress at a site on the structure orapparatus that is distal to the actuator. In another embodiment, theapparatus amplifies the volumetric or dimensional change induced by theactuator, while in another embodiment, the apparatus deamplifies thevolumetric or dimensional change induced by the actuator.

In one embodiment, the structure or apparatus moves in or beyond theatmosphere. In one embodiment, such a structure or apparatus may be anaircraft, a missile, a spacecraft or a satellite. In another embodiment,such a structure or apparatus may be part of an aircraft, a missile, aspacecraft, a worm, a robot or a satellite. In other embodiments, thepart may be a wing, a blade, a canard, a fuselage, a tail, an aileron, arudder, an elevator, a flap, a pipe, a propellor, a mirror, an opticalelement, or a combination thereof. In other embodiments, the part may bean engine, a motor, a valve, a regulator, a pump, a flow control device,a rotor, or a combination thereof.

In another embodiment, the structure or apparatus moves in water. In oneembodiment, such a structure or apparatus may be a boat, a ship, asubmarine or a torpedo. In another embodiment, the structure orapparatus is a part of a boat, a ship, a submarine or a torpedo. Inanother embodiment, the part is a blade, a rudder, a pipe, a propellor,an optical element, or a combination thereof. In another embodiment, thepart is an engine, a motor, a valve, a regulator, a pump, a flow controldevice, a rotor, a switch or a combination thereof.

In another embodiment, the structure or apparatus is a bomb, a means oftransportation, an imaging device, a robotic, a worm, a prosthesis, anexoskeleton, an implant, a stent, a valve, an artificial organ, an invivo delivery system, or a means of in vivo signal propagation.

In another embodiment, this invention provides a method of actuation,comprising the step of applying a voltage or current to an actuatorcomprising a negative electrode, a positive electrode and anintercalating species, wherein controlling the applied voltage orcurrent induces intercalation of the intercalating species in theactuator, whereby the intercalation induces a volumetric or dimensionalchange of said actuator. In one embodiment, an apparatus or structurecomprises the actuator. In one embodiment, the method results in astructural change in the structure or apparatus comprising the actuator.In another embodiment, the structure or apparatus comprises more thanone actuator. In another embodiment, a curvature, bend or twist, orcombination thereof is induced in the structure or apparatus.

In another embodiment, this invention provides a method of producingtorque or rotary motion in an apparatus comprising a RotationalElectrochemical Actuator, comprising the step of applying a voltage to aRotational Electrochemical Actuator comprising an negative electrode, apositive electrode and an intercalating species, wherein applyingvoltage causes current flow inducing intercalation of the intercalatingspecies in the actuator resulting in a volumetric or dimensional changeof the actuator such that the rolled laminate layers unwind, and torqueor rotary motion is produced.

In another embodiment, this invention provides a pump comprising atleast one electrochemical actuator, comprising an negative electrode, apositive electrode, an intercalating species, and at least one valve,wherein following application of a voltage causing current flow in saidactuator, intercalation of said species produces a change in volume insaid actuator, such that fluid is directed through said valve. In oneembodiment, the pump comprises a series of actuators. In one embodiment,the actuators are placed in a parallel series. In another embodiment,the actuators are placed in a plane so as to direct fluid throughdesigned channels.

In another embodiment, this invention provides a nastic structurecomprising at least one electrochemical actuator, comprising an negativeelectrode, a positive electrode, and an intercalating species, whereinfollowing application of a voltage causing current flow in the actuator,intercalation of the intercalating species produces a change in volumein the actuator, such that a bend or other deformity is induced in thenastic structure.

In another embodiment, this invention provides for the use of anelectrochemical actuator in a microfluidic system, wherein a network ofhydraulic actuators is driven by intercalation-induced volume changes inthe electrochemical actuator.

In another embodiment, this invention provides for the use of at leastone electrochemical actuator for flight control of an aircraft, whereinthe actuator is positioned on the aircraft, such that followingintercalation-induced volume changes in the actuator(s), greater flightcontrol is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A demonstrates an embodiment of a reversible lithium intercalationwith phospho-olivines Li(Fe,Mn)PO₄ to produce large intrinsic(crystallographic) volume changes of 7.4-10% [A. Yamada et al., J.Electrochem. Soc., 148, A224 (2001)]. FIG. 1B depicts the expansion upondischarge detected following Li+ intercalation into an LiFePO₄ positiveelectrode in an actuator with a 100 μm active layer, producing a 2.3%linear strain, well in agreement with the predicted value, in thisembodiment of the invention. FIG. 1C depicts the actuation strain in amultilayer Li-polymer battery of ˜5 mm thickness. Strain was measurednormal to the plane of the multilayer stack during charge and discharge.The 50 mm reversible displacement corresponds to ˜1% linear strain.

FIG. 2 demonstrates an embodiment of a multilayer stackedelectrochemical actuator comprised of Li ion-polymer batteries (ATLCorporation). According to this aspect of the invention, the elastic(Young's) modulus measured normal to the face of the cells (in thedirection of layer stacking) was very low, ˜30 MPa.

FIG. 3 graphically depicts the charge-discharge voltage curves andcorresponding strain, obtained under various pre-stress conditions, foractuators of one embodiment of a multilayer stacked design. Maximumstrain was ˜0.7% and obtained actuation energy density was ˜12 kJ/m³.

FIG. 4 graphically depicts the charge-discharge voltage curve andcorresponding strain, obtained under 3.5 MPa constant pre-stress, foractuators of one embodiment of a multilayer stacked design. Strain is˜1% and actuation energy density is ˜35 kJ/m³.

FIG. 5 shows embodiments of lithium ion rechargeable cells based onLiCoO₂-carbon chemistry, with different internal constructions.

FIG. 6 graphically depicts the volume reduction of an embodiment of amultilayer stacked actuator cells prior to and following isopressingtreatment at 45,000 psi.

FIG. 7 graphically depicts viscoelastic relaxation of applied stress inan embodiment of a multilayer stacked actuator. Relaxation in appliedstress is measured as a function of time in cells subjected to 10 MPastress in an Instron test machine.

FIG. 8 graphically depicts the volume expansion of an embodiment of amultilayer stacked actuator having 150 mAh charge capacity, measured byfluid displacement.

FIG. 9 graphically depicts the cyclic charge/discharge and correspondingstrain of two embodiments of multilayer stacked actuators under 5 MPauniaxial stress.

FIG. 10 graphically depicts the cyclic actuation tests of an embodimentof a multilayer stacked actuator at 5 and 10 MPa uniaxial stress.

FIG. 11 graphically depicts the cyclic actuation tests of an embodimentof a multilayer stacked actuator at 15 and 20 MPa uniaxial stress.

FIG. 12 graphically depicts the strain and energy density of embodimentsof multilayer stacked actuators as a function of uniaxial prestress.

FIG. 13 graphically depicts strain versus cycle number for constantcurrent cycling of an embodiment of a multilayer stacked actuator at thegiven current for 1 and 2 minutes under 2 MPa constant stress.

FIG. 14 graphically depicts strain versus cycle number for constantcurrent cycling of a multilayer stacked actuator at the given currentfor 5 and 10 minutes under 2 MPa constant stress.

FIG. 15 shows strain versus the utilized reversible capacity in anembodiment of a multilayer stacked actuator under 2 MPa constant stress.

FIG. 16 depicts an embodiment of a bi-layer stacked actuator fabricatedfrom densified single-layer coatings of LiCoO₂ and graphite electrodes.

FIG. 17 graphically depicts a charge-discharge voltage curve andcorresponding strain measured in an embodiment of a bi-layer stackedactuator under 1 MPa constant prestress. Measured strain is 3-4% andactuation energy density is ˜45 kJ/m³.

FIG. 18 graphically depicts a charge-discharge voltage curve andcorresponding strain measured in an embodiment of a bi-layer stackedactuator under 10 MPa constant pre-stress. Measured strain is 2.5-3% andactuation energy density is ˜300 kJ/m3.

FIG. 18 shows actuation strain versus charge/discharge for bilayerstacked actuator, at 10 and 17 MPa applied uniaxial stress.

FIG. 19 shows actuation strain versus charge/discharge for an embodimentof a bilayer stacked actuator, at 10 and 17 MPa applied uniaxial stress.

FIG. 20 shows strain vesus charge and discharge at 1 MPa stress in anembodiment of a multilayer actuator, 6 mm thick, utilizing high densityelectrodes and a microporous polymer separator.

FIG. 21 shows strain vesus charge and discharge at 5 MPa stress in anembodiment of a multilayer actuator, 6 mm thick, utilizing high densityelectrodes and microporous polymer separator

FIG. 22 shows strain vesus charge and discharge at 10 MPa in anembodiment of a multilayer actuator, 6 mm thick, utilizing high densityelectrodes and microporous polymer separator.

FIG. 23 depicts an embodiment of an actuator comprising multiple squareposts laser-micromachined from electrochemical actuation material, herehighly oriented pyrolytic graphite (HOPG) with the c-axis directionaligned with the post axis (longitudinal direction). An LiCoO₂ lithiumsource is placed adjacent to HOPG posts allowing intercalation of thegraphite in the transverse direction, in this embodiment.

FIG. 24 graphically depicts the actuation strain measured uponintercalation of lithium into one embodiment of an HOPG-based actuatorunder 100 MPa constant pre-stress. Actuation energy density is ˜1000kJ/m³.

FIG. 25 is an SEM image of an array of posts machined in a piece of HOPGforming active elements of an embodiment of an electrochemical actuator,and schematic side view of the actuator assembly.

FIG. 26 shows strain versus discharge/charge voltage for an HOPGactuator under 100 MPa applied stress (1 metric ton per cm2) (A), andstrain versus charging voltage for an HOPG laser micromachined actuatorunder 50 MPa applied stress (B).

FIG. 27 schematically depicts an embodiment of an alternate post designfor a multi-post actuator.

FIG. 28 schematically depicts an embodiment of a large strokeelectrochemical lever actuator.

FIG. 29 shows actuator output strain for an embodiment of anElectrochemical Lever Actuator using a stack of ten 200 mAh cells,cycled at 1 C rate under 270 N load, resulting in 4 MPa preload on theactive elements.

FIG. 30 schematically depicts views of weave actuator with main parts:(1) active elements, (2) top and bottom fibers and (3)constant-curvature caps.

FIG. 31 depicts an experimental setup for a test of an embodiment of anelectrochemical woven actuator and results from test, with actuatorstrain and active element strains shown.

FIG. 32 graphically depicts the theoretical stiffness and maximum-strainbounds of an embodiment of the EWA as a function of the ratio of itslength (L) and the active element length (w). Actual test results areshown as stars on the figure.

FIG. 33 depicts an embodiment of an actuated beam utilizing 27electrochemical actuators of type shown in FIGS. 2-4, electricallyconnected in parallel. Layers of fiberglass weave constrain thedeformation of the beam on the lower surface. When one end (the base) ofthe beam was clamped, the tip of the beam was observed to deform 1 mmupon charging or discharging the batteries, corresponding to a surfacestrain of 400 microstrain.

FIG. 34 schematically depicts actuation in a fluidic system, comprisingan electrolytic membrane, which pumps an ion from one side to another,producing high actuation forces. In one embodiment, R1 is not equal toR2.

FIG. 35 schematically depicts an example of an actuator comprising apositive electrode, separated from an negative electrode by a separator,where the height of the actuator is 200 μm.

FIG. 36 is an additional schematic depiction of one embodiment of thisinvention, showing an actuator 10 comprising a positive electrode 12, inthis case LiMPO₄, where M is any metal, separated from an negativeelectrode 14 by a separator layer 16, and both negative electrode andpositive electrode current collectors, 18 and 20, respectively, attachedto a power source 22, supplying 4 V. The actuator possesses 200 μm stackthickness, and an E value of 2×10⁴ V/m.

FIG. 37 schematically depicts one embodiment of a solid-state thin-filmbattery (24) that can be used for actuation. The negative electrode 28is separated from the positive electrode 30 by an electrolyte layer 32,and current collectors for the negative electrode 34 and positiveelectrode 36 as well as the other components of the actuator arepositioned on a substrate 26. A protective coating 38 covers theactuator, providing a height of 15 μm, in this example.

FIG. 38 schematically depicts embodiments of a Multilayer StackedActuator of this invention. In this example, a high stiffness bilayersubassembly 40 and multilayer-stacked assembly 54 are depicted. Becausethe system is composed of ceramic layers 44, 46 and metal electrodes 42,the stack will have high stiffness and a strain capability of severalpercent. Liquid electrolyte may infiltrate the actuator 48. Currentcollectors 38, 50 may be present, with a power source 52, as indicated.This actuator would be an all-purpose, high energy density actuator,which could be used in many applications requiring high energy densitiesat modest bandwidth.

FIG. 39 schematically depicts a Rotational Electrochemical Actuator 56,comprising laminates of current collectors 58, negative electrodes 60,positive electrodes 62, and a separator 64. A structural aluminum layer66 is added and the Rotational Electrochemical Actuator is infiltratedwith electrolyte 68. The actuator may be assembled as a spiral 70,around an inner mandrel 72, and covered by an outer shell 74.

FIG. 40 schematically depicts an embodiment of a Continuous FiberElectrochemical Actuator 76 comprised of a fiber composite system, inwhich the active fibers form the negative electrode 78. The fibernegative electrode is separated from the positive electrode 80, by apolymer or inorganic separator 82, and a liquid or solid electrolytelayer 84. Current collectors 86 and 88, respectively, are connected tothe power source 90 in the actuator.

FIG. 41 schematically represents another embodiment of a ContinuousFiber Electrochemical Actuator 92 comprised of individual negativeelectrode fibers 94, coated with a ceramic or polymer electrolyte 96 anda lithiated positive electrode 98, connected to a power supply 100.These fibers can form an active fiber composite 102.

FIG. 42 depicts an embodiment of an adaptive structure or apparatus 104comprising an electrochemical actuator of this invention 106, mounted onits surface 108 (FIG. 10A). In one embodiment, the integration of anactuator within a structure or apparatus 110 may be as schematicallydepicted in FIG. 10B. The electrochemical actuator, or in anotherembodiment, actuators 140, may be in one embodiment, thin film, or inanother embodiment, thick film laminated electrochemical actuators,which may be oriented normally to the surface, and may be positionedwithin a stiff surface layer 120, on a substrate 130. Changing theaspect ratio of the expanding and contracting elements of the actuatorsand strategic positioning may produce greater deformation in the surfaceplane, in another embodiment, as schematically diagrammed in FIG. 10C,via the positioning of the positive electrode 150 and the negativeelectrode 160, in another embodiment, which may be evident when viewedlooking down the plane of the surface, or in cross-section (10D).

FIG. 43A schematically depicts one embodiment of an actuator 170comprising a carbon or lithium negative electrode 200, which expandswhen lithiated, and a LiMn₂O₄ or LiFePO₄ positive electrode 190, whichcontracts when de-lithiated, which if bonded to a separator 180, willproduce a marked bend in the entire structure. One embodiment of such ause would be in an airfoil 210 where the actuator is positioned, suchthat the negative electrode is facing outward 230, from the surface 220,such that following actuation, a greater curvature outward occurs (43B).FIG. 44C schematically depicts a structure 240 comprising a siliconwafer 250 that can be lithiated from the surface 260, via the lithiummetal or lithiated oxide electrode as the lithium source, in order toinduce volumetric expansion hence bending.

FIG. 44A schematically depicts one embodiment of a structure orapparatus 280 made to bend around more than one axial direction, byhaving an array of electrochemical actuators 300 on the surface of thestructure or apparatus 290. FIG. 44B depicts an example of how actuatorsmay be utilized to unfurl a wing.

FIG. 45 schematically depicts an assembly 310 of possible arrangementsof actuators 320 on the wings 330 of an aircraft, which may providetwist to the wing.

FIG. 46A schematically depicts a microfluidic pump 340, comprising apositive electrode 350, and negative electrode 360, separated by aliquid electrolyte layer 370. The actuator undergoes a net volume changeupon charging and discharging 390, enabling fluid propulsion through thevalves 380. A pump or microfluidic device 400 comprising a series ofactuators 410, which upon charging and discharging induces fluid flowfrom intake 420, through exit 430 of the pump (B). Positioning of theactuators is such that channels are designed (14C).

FIG. 47 schematically depicts multiple morphing capabilities of theactuators or structures comprising the same of this invention.

FIG. 48 depicts embodiments of a morphing plate architecture envisionedfor this invention. In A, an overall plate architecture, with 3 actuatororientations is shown. In B, an embodiment depicting an embeddedindividually addressable multilayer stack actuator array is shown. In C,an embodiment depicting a distributed array of electrochemical fiberactuators applying tensile loads is shown. In D, embodiments depictingactuator designs, which allow for greater expansion or contraction, areshown.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides, in one embodiment, methods andstructures/apparatuses for actuation that is based on the electric fielddriven intercalation (ion-exchange) of high-modulus inorganic compoundsand produces true, useful, mechanical work.

The invention provides, in one embodiment, an electrochemical actuator,comprising a negative electrode, a positive electrode and anintercalating species, wherein the electrochemical actuator is subjectedto an applied voltage or current, whereby application of the voltage orcurrent or cessation thereof induces intercalation of the intercalatingspecies in the actuator, resulting in a volumetric or dimensional changeof the actuator. In the context of this invention, and in oneembodiment, intercalation is understood to have a broad meaningincluding the insertion of ions into a structure causing a dimensionalchange without substantially changing the arrangement of other atoms,insertion forming a disordered or ordered solid solution, insertionforming an alloy, or insertion causing a partial or completetransformation to a new phase. All of these methods of “intercalation”may be useful in providing mechanical actuation.

Solid-state ion insertion compounds used in battery systems may undergolarge and reversible volume changes (up to ˜15% with high reversibility)as ions (e.g., Li+) are intercalated into the structure, which isexploited by the actuators of this invention, in one embodiment. As oneexample, FIG. 1 shows the volume changes that occur in the olivinestructure compound (Fe,Mn)PO₄ as it is lithiated to the endmembercomposition Li(Fe,Mn)PO₄. Between the fully lithiated (upper curve) andfully delithiated (lower curve) limits of composition, a volume changeof 7.4-10% (linear strain of 2.4-3.2%) is realizable depending on theFe/Mn ratio. This is just one of numerous new intercalation compoundsthat have emerged from the battery field, which have promise for thetechnology here proposed, all of which represent embodiments of thisinvention. The insertion of ions into such compounds can result involume expansion or contraction, and such expansion or contraction canbe isotropic or anisotropic.

The volume change may have a corresponding linear or multiaxialdimensional change that is here exploited for mechanical actuation.Where the dimensional change is anisotropic, the anisotropy may befurther exploited to maximize, minimize, or optimize the dimensionalchange for actuation, by using said compounds in a form in which thereis a crystallographic orientation of the compound in the desireddirections of actuation. For example, in one embodiment in whichgraphite is the active material, the expansion upon intercalation ofalkali ions occurs primarily normal to the graphene planes of thegraphite structure, and maximum expansion and contraction can beproduced by having the graphene planes of the graphite oriented in thedesired directions of actuation.

Table 1 provides exemplary pairs of compounds comprising anelectrochemical couple with reversible electrochemical insertion oflithium, for which values for intrinsic linear and volumetric expansions(i.e., crystal constants of the lithiated and delithiated forms) areavailable. Table 2 provides exemplary individual compounds used aspositive and negative electrodes in lithium batteries, and the volumechange that occurs for a typical composition to which the compound canbe delithiated. Note that in the electrochemical actuators of thisinvention, compounds are not restricted to being used as the electrodethat they would comprise in a battery designed for optimal energystorage; that is, the active materials may comprise either positive ornegative electrode in an electrochemical actuator. TABLE 1 Cell Voltageand Net Volume Change For Charge-Balanced Cells Using Graphite as OneElectrode Net Volume Change Electrochemical Charging Cell (Positiveelectrode + Reaction for Cell Voltage Negative electrode) LiCoO₂ + 3C →Li_(0.5)CoO₂ + 3.6 V +5.8% 0.5LiC₆ LiNiO₂ + 4.2C → Li_(0.3)CoO₂ + 3.7 V+5.3% 0.7LiC₆ LiFePO₄ + 6C → FePO₄+ LiC₆ 3.3 V +5.8% LiMn₂O₄ + 6C →Mn₂O₄ + LiC₆ 3.8 V +4.2% Li + 6C → LiC₆ 0.15 V  −2.4%

TABLE 2 Selected Lithium Storage Electrodes and Associated VolumeChanges Lithium Insertion Limiting Compound Composition* ΔV/V_(o)Comments Positive electrodes LiCoO₂ Li_(0.5)CoO₂ +1.85% Y˜400 GPa.LiFePO₄ FePO₄ −7.35% Y˜150 GPa. LiNiO₂ Li_(0.3)NiO₂ −2.82% LiMn₂O₄ Mn₂O₄−7.35% Negative electrodes Li_(4/3)Ti_(5/3)O₄ Li_(7/3)Ti_(5/3)O₄ 0“Zero-strain” spinel structure electrode. C ⅙ LiC₆ +13.1% Y˜15 GPa(polycrystal). Si Li_(4.4)Si  +312% β-Sn Li_(4.4)Sn  +260%*For reversible cycling, except for Si and Sn

LiCoO₂, when used as the positive electrode, expands 1.85% when lithiumis removed, while most other compounds shrink. Despite a modest volumechange, LiCoO₂ is of interest because it can be used with carbon(Table 1) in a highly reliable and well-developed electrochemicalsystem. LiCoO₂ has a hexagonal structure (rhombohedral space group R-3m)in which the lithium planes are parallel to the c-axis. The Young'smodulus along the c-axis is 330 GPa while that along the a-axis (whichlies in the fast-diffusion plane) is 500 GPa (F. X. Hart and J. B.Bates, J. Appl. Phys., 83[12], 7560 (1998)), hence an aggregate valuefor randomly-oriented polycrystals of ˜400 GPa can be obtained. Such avalue is close to that obtainable for high strength structural ceramicssuch as Al₂O₃ and SiC.

A second example for use as the positive electrode is LiFePO₄, aphospho-olivine that when suitably doped (S. Y. Chung, J. T. Bloking,Y.-M. Chiang, Nature Materials, 1, 123 (2002)) has extremely fastcharge-discharge behavior for a lithium battery, retaining ˜50% of itscharge capacity (and crystal expansion) at charge-discharge times of ˜1min (17 mHz). Its elastic properties have not been measured, but thesimilar mineral phosphate apatite (Ca₅(OH, F)(PO4)₃) has a Young'smodulus of 150 GPa (G. Simmons and H. Wang, Single Crystal ElasticConstants and Calculated Aggregate Properties, MIT Press, Cambridge,Mass., 1971). It is expected that the phospho-olivines will have ahigher modulus than apatite due to their denser atomic packing. Anotherattraction of these compounds is their safety in electrochemicalsystems.

As shown in Table 2, graphite is an excellent candidate for use as thenegative electrode of an electrochemical actuator, owing to its ˜13%volume expansion upon lithiation to the limiting composition LiC₆. Thisfamily includes not just graphite but also various other forms ofdisordered carbons, which together constitute widely used negativeelectrodes in current technology (see for example N. Imanishi, Y. Takedaand O. Yamamoto, and by M. Winter and J. O. Besenhard, Chapters 5 and 6respectively in Lithium Ion Batteries, Eds. M. Wakihara and O. Yamamoto,Wiley-VCH, Weinheim, Germany, 1998)).

Using materials from Table 2, several types of electrochemical actuatorsare conceived. In one, the volume change of one electrode material isused to perform mechanical work, while the volume change in thecounterelectrode is either negligible or is accommodated in a non-loadbearing manner. In this instance active materials are selected primarilyaccording to their elastic constants and strains.

In a second type, both the positive electrode and negative electrode areload-bearing, and volume changes in both active materials in theelectrochemical couple (the positive electrode and the negativeelectrode) are used, the net volume change of the electrochemicalreaction being the relevant quantity. Table 1 lists severalelectrochemical couples that use carbon as the negative electrodematerial, from which it is seen that several options give ˜5% volumetricstrain in a cell where the relative amounts of each material areadjusted to give a charge-balanced cell. In both designs, other issuessuch as rate capability (bandwidth), reversibility in cycling, andstability and safety over a wide range of operating temperatures mustalso be considered in the selection process.

Using the materials of Table 2, it is also possible to design actuatorsof a type that expands upon charging of the electrochemical cell, or onethat expands upon discharging. Table 1 provides four examples thatexpand upon charging of the cell and one that expands upon discharging.As another example of actuators that expand upon discharging, anyelectrode-active compound that has a lithium insertion potential lowerthan that of the “zero-strain” material Li₄Ti₅O₁₂ (Table 2), and whichexpands upon lithiation, will comprise the negative electrode when usedwith Li₄Ti₅O₁₂. Such a cell will spontaneously discharge when electronsare allowed to flow between the the electrodes, and lithium will migratefrom the Li₄Ti₅O₁₂ to the other electrode, causing it to expand. Havinga cell that either expands or contracts upon spontaneous discharge canbe advantageous in designing the actuators of the invention forapplications where a particular “default” state is desirable, forexample in designing an actuated latch that defaults to an open (orclosed) state in the event of an intentional or accidental short-circuitof the electrochemical actuator.

The stress that an actuator can be subjected to while producing usefulstrain, or the “blocked stress” that can be produced by an actuatorundergoing zero or small strain, are important performancecharacteristics that bear directly on the practical utility of theactuator. In this respect, Table 2 and earlier discussion illustrates aparticular advantage of the electrochemical actuators of the invention,which is the high elastic modulus of the active materials. In thisinvention we recognize and design actuators to utilize the fact thatelectrochemically-induced strains are substantial, and at the same timemany ion-storage compounds including graphite, metal alloys, andintercalation oxides have high elastic modulus (50-150 GPa), more than athousand times greater than other actuator materials such aselectroactive polymers or gels, thereby providing for large actuationauthority as well as large strain.

In addition to high actuation energy density and actuation stress, onemeasure of actuation authority that permits comparisons withpiezoelectric actuator technology is the coefficient e³³, which refersto actuation stress generated per unit electric field (Units:Pa/V/m=C/m²). (In the case of piezoelectrics, this coefficient ismaximized for stresses in the direction of the applied electric fields,signified by the superscript “33.”). Consider a laminatedelectrochemical actuator having cathode and anode thicknesses comparableto those in current lithium ion battery technology, as schematized inFIG. 37. As an example such a device may have an intercalation compoundas one electrode, a stiff but porous ceramic separator, and an inorganicnegative electrode of high elastic modulus, as shown in FIG. 38. For a200 micrometer thick layer (typical for battery electrodes) of theelectrochemical insertion compound in FIG. 1, when formulated as apowder-based composite electrode, will have a Young's modulus of Y=50GPa (assumed to be reduced from the single crystal value of ˜150 GPa).Under 3.3V applied voltage this electrode can be fully intercalated toreach a linear strain of ε˜1.5%, thereby generating e³³=3.8×10⁴ C/m².This value considerably exceeds the e³³ values obtained with thebest-known piezoelectrics, of 15-40 C/m². The corresponding actuationspecific energy, taken as ½Yε²/ρ, the strain energy density, taken as½Yε ²/ρ where ρ is the material density, is about 2050 J/kg (5.6×10³kJ/m³) for the active material layer, and ˜1000 J/kg (2.8×10³ kJ/m³) foran actuator stack containing one-half by weight or volume of inactivesupporting layers. These values also greatly exceed typical values of13.5 J/kg and 100 kJ/m³ for a PZT piezoelectric ceramic. At a stackvolumetric strain energy density of 2.8×10³ kJ/m³, and 1.5% linearstrain, the equivalent blocked stress is ˜375 MPa. These comparisonsillustrate the advantages of the present invention over existingactuation technology where high actuation energy, high actuationauthority, and large strain is required, and their usefulness in a widevariety of adaptive structures requiring significant strain coupled withhigh authority.

Since batteries are energy storage devices, the total amount of storedelectrical energy is naturally maximized; typical stored energy levelsfor unpackaged rechargeable lithium ion batteries (i.e., the active“stack” alone without the can) are 550 Wh/liter and 200 Wh/kg. In suchcases, and even in electrochemical actuators of the invention designedwithout regard to electrical energy storage and operating at less than1V or even less than 0.5V applied voltage, during a charge/dischargecycle the mechanical work done may be only a few percent of the totalelectrical energy stored. This low level of electromechanical couplingis largely responsible for the high blocked stresses that areachievable, i.e. discharging a charged battery through the applicationof an external stress is difficult. In one embodiment, the actuator isdesigned such that the electrical energy is shuttled from the actuatorto a storage battery, or in another embodiment, between two actuatorsacting in concert so that as one is charged the other is discharged, andthe positive and negative strains simultaneously produced add to producea desired deformation. In one embodiment, the invention allows for theuse of antagonistic actuators so that as one is charged, another isdischarged, having both act beneficially from the point of view ofstrain while shuttling the electrical energy between the two so that itis not resistively dissipated. Thus, according to this aspect of theinvention, the losses in the system may be primarily the low resistivelosses that are produced as the charge is shuttled between actuators.

In one embodiment, the intercalated material refers to an ion insertioncompound, and in one embodiment, a solid-state ion insertion compoundsuch as is used in battery systems, which is intercalated within thestructure of the actuator, as described herein. In another embodiment,the intercalating species is a proton or an alkali metal or an alkalineearth metal. In one embodiment, the alkali metal is lithium.

In another embodiment, the high-modulus inorganic compounds areexemplified by the lithium transition metal oxide positive electrodes(e.g., LiCoO₂, LiMn₂O₄, LiNiO₂, LiFePO₄) and carbon negative electrodesdeveloped as storage electrodes for rechargeable battery systems. These,and in other embodiments, other similar compounds can be intercalatedwith Li+ ions at low voltages of 1.5-5V to produce large and reversiblevolume changes of, in some embodiments, 3-13%.

In another embodiment, the ion insertion mechanisms may make use of analloying of lithium with various metals and metalloids, such as, forexample, Sn, or Si, which, in another embodiment may result in volumeexpansions in excess of 250%.

In one embodiment, the electrochemically-induced strain produced foractuation, when using intercalation compounds, which are oxides of highelastic modulus (50-150 GPa) will allow large actuation authority aswell as large free strain, such that stresses can be producedapproaching the intrinsic compressive strength of the materials.Furthermore, these compounds have low densities (3.5-5 g/cm3) comparedto lead-based piezoelectrics or metal alloys comprising magnetostrictorsand shape memory alloys.

In one embodiment, packaged actuators of this invention may havedensities of 2-4 g/cm³, which can produce high actuation authority,suitable for a broad range of applications.

In one embodiment, the volumetric or dimensional change in said actuatormay range from 0.1-300%. In one embodiment, the volumetric ordimensional change in said actuator may range from 0.1-10%, or inanother embodiment, the volumetric or dimensional change in saidactuator may range from 0.1-50%, or in another embodiment, thevolumetric or dimensional change in said actuator may range from0.1-100%, or in another embodiment, the volumetric or dimensional changein said actuator may range from 1-100%, or in another embodiment, thevolumetric or dimensional change in said actuator may range from10-100%, or in another embodiment, the volumetric or dimensional changein said actuator may range from 1-200%, or in another embodiment, thevolumetric or dimensional change in said actuator may range from10-200%, or in another embodiment, the volumetric or dimensional changein said actuator may range from 50-200%, or in another embodiment, thevolumetric or dimensional change in said actuator may range from100-200%, or in another embodiment, the volumetric or dimensional changein said actuator may range from 10-300%, or in another embodiment, thevolumetric or dimensional change in said actuator may range from100-300%, or in another embodiment, the volumetric or dimensional changein said actuator may range from 50-300%. In another embodiment, thevolumetric or dimensional change in an actuator of this invention may bereversible.

In one embodiment, the volumetric or dimensional change in said actuatormay be a function of the current flow induced by an applied voltage. Inone embodiment, the electrochemical actuator may be subjected to avarying voltage. In one embodiment, increasing the voltage or currentover time may result in a gradual increase in volume. In anotherembodiment, decreasing voltage or current over time results in a gradualdecrease in volume, or in another embodiment, in a gradual increase involume. In another embodiment, cycles of varied voltage may be desiredin order to induce discreet changes in volume.

In another embodiment, an electrode of an actuator of this invention isinitially enriched in, and may serve as a source for, the intercalatingspecies. In another embodiment, a negative electrode of an actuator ofthis invention may serve as a source for the intercalating species. Inanother embodiment, a positive electrode of an actuator of thisinvention may serve as a source for the intercalating species.

In another embodiment, the electrode comprises a high elastic moduluscompound. In another embodiment, an electrode comprises an iontransition metal oxide. In another embodiment, the ion transition metaloxide is a proton or an alkali metal or an alkaline earth metal. Inanother embodiment, the alkali metal is lithium. In another embodiment,an electrode comprises: LiCoO₂, LiFePO₄, LiNiO₂, LiMn₂O₄, LiMnO₂,LiMnPO₄, Li₄Ti₅O₁₂, and their modified compositions and solid solutions.In another embodiment, an electrode comprises: an oxide compoundcomprising one or more of titanium oxide, vanadium oxide, tin oxide,antimony oxide, cobalt oxide, nickel oxide or iron oxide. In anotherembodiment an electrode comprises TiSi₂, MoSi₂, WSi₂, and their modifiedcompositions and solid solutions. In another embodiment an electrodecomprises a metal or intermetallic compound. In another embodiment anelectrode is lithium or a lithium-metal alloy, which may be crystalline,nanocrystalline, or amorphous. In another embodiment the negativeelectrode is one or more of aluminum, silver, gold, boron, bismuth,gallium, germanium, indium, lead, antimony, silicon, or tin. In anotherembodiment, an electrode is carbon in the form of graphite, a carbonfiber structure, a glassy carbon structure, a highly oriented pyrolyticgraphite, a disordered carbon structure or a combination thereof. Inanother embodiment, the intercalating species is an ion. In anotherembodiment, a proton or an alkali metal or an alkaline earth metal.

In another embodiment, the positive or negative electrode compoundsexhibit an elastic modulus ranging between 10-500 GPa. In anotherembodiment, the compound exhibits an elastic modulus ranging between50-150 GPa, or in another embodiment, the compound exhibits an elasticmodulus ranging between 50-350 GPa, or in another embodiment, thecompound exhibits an elastic modulus ranging between 50-450 GPa, or inanother embodiment, the compound exhibits an elastic modulus rangingbetween 10-250 GPa, or in another embodiment, the compound exhibits anelastic modulus ranging between 10-350 GPa, or in another embodiment,the compound exhibits an elastic modulus ranging between 10-450 GPa, orin another embodiment, the compound exhibits an elastic modulus rangingbetween 25-250 GPa, or in another embodiment, the compound exhibits anelastic modulus ranging between 25-500 GPa, or in another embodiment,the compound exhibits an elastic modulus ranging between 50-500 GPa, orin another embodiment, the compound exhibits an elastic modulus rangingbetween 50-300 GPa.

In another embodiment, an electrode comprises an ion transition metaloxide. In another embodiment, said ion transition metal oxide is aproton, alkali metal, or alkaline earth metal. In another embodiment,the alkali metal is lithium. In another embodiment, an electrodecomprises: LiCoO₂, LiFePO₄, LiNiO₂, LiMn₂O₄, LiMnPO₄, Li₄Ti₅O₁₂, ortheir modified compositions or solid solutions. In another embodiment,the intercalating species is an ion. In another embodiment, a proton oran alkali metal or an alkaline earth metal.

In one embodiment, the electrochemical actuators of this invention havea negative electrode or positive electrode, or combination thereof,comprising a single crystal or, in another embodiment, a polycrystalhaving preferred crystallographic orientation of its crystallites. Inanother embodiment, the electrochemical actuators of this invention havea negative electrode or positive electrode, or combination thereof,comprising a multiplicity of individual crystallites or a powder. Inanother embodiment, the multiplicity of individual crystallites or apowder, wherein there is a preferred crystallographic orientation of thecrystallites or powder particles. In another embodiment, theelectrochemical actuators of this invention have a negative electrode orpositive electrode, or combination thereof, comprising a multiplicity ofparticles of an amorphous or disordered material.

In another embodiment, an actuator of this invention further comprises acurrent collector, which, in another embodiment, comprises a conductivematerial. In another embodiment, an actuator of this invention furthercomprises a separator that is electronically insulating, which in oneembodiment is porous, or in another embodiment, is rigid. In oneembodiment, the porous separator comprises a microporous polymer. Inanother embodiment, the porous separator comprises a porouselectronically insulating ceramic material, which in another embodiment,is alumina, an aluminosilicate, cordierite, or a silicate glass. Inanother embodiment, the electrodes of an actuator of this inventionfurther comprise a conductive additive.

In another embodiment, an actuator of this invention further comprisesan electrolyte. In one embodiment, the electrolyte is a solidelectrolyte, or in another embodiment, the electrolyte is a liquid orgel electrolyte. In another embodiment, an actuator of this inventionfurther comprises an external packaging layer, which may be, in oneembodiment, an electrochemically-insulating layer, or, in anotherembodiment, a protective layer or, in another embodiment, a combinationthereof.

In one embodiment of the invention, intercalation of the species in anactuator of this invention can occur upon both application of thevoltage and cessation thereof. In one embodiment, the applied voltage isin a range of between 0.1-15 V. In another embodiment, the appliedvoltage is in a range of between 1-5V. In another embodiment, theapplied voltage is in a range of between 0.1-5 V. In another embodiment,the applied voltage is in a range of between 1-10 V. In anotherembodiment, the applied voltage is in a range of between 1-15 V. Inanother embodiment, the applied voltage is in a range of between 5-15 V.In another embodiment, the applied voltage is in a range of between 5-10V. In another embodiment, the applied voltage may be varied, which may,in another embodiment, influence the amount of intercalation, and inanother embodiment, the degree of volume change.

In another embodiment, the volumetric or dimensional change in anactuator of this invention is in the negative electrode or positiveelectrode or a combination thereof. In another embodiment, thevolumetric or dimensional change is reversible. In another embodiment,intercalation in an actuator of this invention produces high strain.

In one embodiment, the strain produced ranges from 0.1% to 300%, or inanother embodiment, the strain produced ranges from 1% to 300%, or inanother embodiment, the strain produced ranges from 10% to 300%, or inanother embodiment, the strain produced ranges from 0.1% to 200%, or inanother embodiment, the strain produced ranges from 10% to 300%, or inanother embodiment, the strain produced ranges from 10% to 200%, or inanother embodiment, the strain produced ranges from 50% to 300%, or inanother embodiment, the strain produced ranges from 50% to 200%.

In another embodiment, a negative electrode, or in another embodiment, apositive electrode, in an actuator of this invention serves as a donoror acceptor or combination thereof of an intercalating species.

The electrochemical actuators of the invention may have many differentconstructions or designs or architectures. In some embodiments they maybe implemented with constructions similar to storage batteries. In oneembodiment, in a form similar to a thin-film battery, as schematicallydepicted in FIG. 37. The actuator 24 may be positioned on a substrate26. The actuator comprises a negative electrode 28, and a positiveelectrode 30, which is separated from the negative electrode by anelectrolyte layer 32. In one embodiment, the electrolyte is a solidelectrolyte, or in another embodiment, a liquid electrolyte. Currentcollectors for the negative electrode 34 and positive electrode 36 mayalso be provided. A protective coating 38 may be present as well, whichmay comprise an insulating material.

In other embodiments, the actuator may have a design that is similar tomultilayered storage batteries of either stacked or wound designs orhybrids thereof, including for example designs where a separator film iscontinuously wound around a series of sequentially stacked discreteelectrodes. Such designs are well-known to those skilled in the art ofbatteries. In one embodiment, the invention provides a MultilayerStacked Electrochemical Actuator, comprising two or more negativeelectrode layers, two or more positive electrode layers, and anintercalating species, wherein the Multilayer Stacked ElectrochemicalActuator is subjected to an applied voltage, whereby application of thevoltage or cessation thereof induces intercalation of the intercalatingspecies in the actuator, resulting in a volumetric or dimensional changeof the actuator.

Electrodes may be fabricated for the actuators of the invention bymethods similar to those used for storage batteries. In one embodiment,according to this aspect of the invention, the active materials may becast from powder-based suspensions containing a polymer binder andconductive additive such as, in one embodiment, carbon, then calendered(rolled) under high pressure (for example, several tons per linear inch)to densely compacted layers in which the volume percentage of activematerial is between 50 and 70%.

In one or more embodiments, a multilayer stacked or woundelectrochemical actuator may use a porous polymer separator film similarto those used in storage batteries.

As exemplified herein, multilayer electrochemical actuators of thisinvention that use a construction similar to those of storage batteries,in particular having electrodes containing polymer binder and liquid orgel electrolyte, having a porous polymer separator that is load bearingduring the function of the actuator, or having external packaging thatcomprises relatively low modulus polymer materials, will, in someembodiments, have a soft construction compared to other actuators of theinvention, due to the low modulus materials used and/or excess internalvolume in the multilayer actuator. Under mechanical load, such actuatorsmay exhibit, in some embodiments, plastic deformation or viscous creepor viscoelastic deformation. In order to obtain useful mechanical workfrom such actuators, according to one aspect of the invention,electrochemical actuators of such design may be mechanically pretreatedor processed so as to provide greater stiffness, higher actuation energydensity, higher actuation strain, decreased creep deformation, lowerhysteresis of strain, improved reversibility of actuation performanceover multiple actuation cycles, or a combination thereof. In oneembodiment, a multilayer actuator is subjected to a hydrostatic pressureto consolidate the actuator, remove free volume, and improveperformance. In another embodiment, a uniaxial stress is applied to themultilayer actuator normal to the layers to remove excess internalvolume, to consolidate the stack, increase the stiffness of theactuator, or to remove creep deformation. Such applied stresses ofhydrostatic or nonhydrostatic nature cannot typically be increasedwithout limit, as internal shorting of the electrode layers or currentcollectors or tabs may occur. Even at stresses not sufficient to causeinternal short circuits, microporous polymer separators orparticle-based electrodes may be consolidated to an extent that inhibitsthe function of the actuator. However, surprisingly it was found asexemplified herein, that a very high preconditioning pressure may beapplied to a multistack actuator to improve its performance withoutcausing internal failure.

Thus in some embodiments, a uniaxial or hydrostatic pressure is used forpreconditioning of an assembled laminated actuator. In some embodiments,the applied pressure may be as high as 10,000 psi (69 MPa), in otherembodiments as high as 20,000 psi (138 MPa) or as high as 30,000 psi(207 MPa), or even as high as 45,000 psi (310 MPa), without causinginternal failure and improving the performance of the actuatorthereafter.

In other embodiments of laminated electrochemical actuatorsincorporating a microporous polymer separator layer between activematerial electrodes, high mechanical energy densities and high strainsare obtained under substantial applied stresses. As illustrated by theExamples, in some embodiments such multilayer stacked actuators are usedto provide actuation strains from 0.5% to 5% under stresses from 0.1 MPato 50 MPa and provide actuation energy densities from 1 to 400 kJ/m³.For one exemplary actuator and conditions of operation, 4% strain isobtained while actuating under 1 MPa stress, providing 40 kJ/m³ energydensity, and 2.5% strain is obtained while actuating under 10 MPastress, providing 250 kJ/m³ energy density. In other Examples andembodiments lower strains and associated stresses and energy densitiesare obtained that provide the ability to conduct useful mechanical work.

In some embodiments an actuator of the invention provides high actuationspeed. In some embodiments, an actuator of similar construction to ahigh charge and discharge rate battery is provided, in whichsubstantially complete charging or discharging of the cell is possiblein less than 6 minutes (10 C rate of charging or discharging), or lessthan 4 min (15 C rate), or less than 3 min (20 C rate). In other suchembodiments, ion storage (faradaic) electrode materials are known thatare capable of substantially complete charge and discharge in as shortas 18 sec (200 C rate), allowing a comparable rate of actuation in anelectrochemical actuator using such materials. In some embodiments, therate of actuation is increased by charging or discharging over timesthat permit only a portion of the total or reversible charge capacity ofthe actuator to be reached.

As illustrated by the Examples, in some embodiments greater than 1.5%under an applied stress greater than 0.5 MPa, greater than 1.5% as highas 4% under stresses as high as 5 MPa, or as high as 2.5% under stressesas high as 20 MPa, providing for actuation energy densities as high as400 kJ/m³. In some embodiments, uniaxial stresses as high as 5 MPa, 10MPa or even 20 MPa may be applied while conducting actuation withoutsignificant loss of actuation energy density or actuation strain or rateof actuation.

In other embodiments, when designing some of the electrochemicalactuators of the invention, use of materials including separators thathave a high elastic modulus, and are capable of withstanding highapplied loads without loss of function are employed. Thus the MultilayerStacked Electrochemical Actuator 40 may be implemented, in oneembodiment, as schematically depicted in FIG. 38. According to thisaspect, in one embodiment, the active layer is the positive electrodelayer 42, which comprises a thick layer, which in one embodiment mayalso comprise a binder. An electronically-insulating, separator layer 44may, in another embodiment, be constructed of a high stiffness porousceramic, such as a silicate based ceramic, or in this case a porousAl₂O₃, as illustrated in FIG. 38. The counter-electrode 46 may beembedded in the porous separator so that it is not load-bearing, in thiscase, Li embedded in the porous Al₂O₃. Liquid electrolyte may beinfiltrated in the actuator 48.

In another embodiment, a high stiffness separator comprises a layer ofelectronically insulating particles, such as particles of an insulatingceramic material. Said layer has greater mechanical flexibility whilemaintaining porosity under high actuation loads. In one embodiment theporous particulate separator is cast as a particulate or slurry layer onthe mating surfaces of one or both electrodes prior to assembly of thelayers, using methods well-known to those skilled in the art of ceramicprocessing or coating technology such as spray deposition, doctor bladecoating, screen printing, web coating, comma-reverse coating, orslot-die coating. In one embodiment the particulate separator comprisesparticles of glass, a silicate ceramic, aluminum oxide,aluminosilicates, or other mixed-metal oxides or nitrides or carbidesthat are electronically insulating.

In another embodiment, the counter electrode 46 may be replaced by anintercalation compound-embedded within a rigid separator, or in anotherembodiment, by a layer that is mechanically functional. Suchsubstitutions may be utilized in a stacked actuator design, 50. Thepower source 52 may be connected to aluminum 38, and copper 52 currentcollectors, respectively. A compact, unitized multilayer actuator 54,such as that demonstrated in this embodiment, may be distributed inadaptive structures in a variety of configurations to impart desireddegrees of freedom. In one embodiment, a device that can be prepared ina reduced-volume state (i.e., by charging or discharging), then insertedinto a structure can be actuated in expansion. Such unitized actuatorscould also be easily replaced, simplifying maintenance of an adaptivestructure.

The energy density of electrochemical actuators (ECAs) may be high, inanother embodiment, and the choice of materials will influence theresulting energy densities obtained. The resulting volume changes mayrange, in one embodiment, from 0.1 to 50%, or in another embodiment,from 0.1 to 1%, or in another embodiment, from 1 to 5%, or in anotherembodiment, from 5 to 8%, or in another embodiment, from 5 to 10%, or inanother embodiment, from 8 to 10%, or in another embodiment, from 10 to15%, or in another embodiment, from 15 to 20%, or in another embodiment,from 5 to 15%, or in another embodiment, from 5 to 20%, or in anotherembodiment, from 20 to 25%, or in another embodiment, from 10 to 20%, orin another embodiment, from 10 to 25%, or in another embodiment, from 20to 35%, or in another embodiment, from 25 to 35%, or in anotherembodiment, from 15 to 35%, or in another embodiment, from 25 to 40%, orin another embodiment, from 25 to 50%, or in another embodiment, from 35to 40%, or in another embodiment, from 35 to 50%.

The electrochemical actuators of this invention, allow for mechanicalenergy production. In one embodiment, any electrochemical actuator ofthis invention, including, for example a Multilayer Stacked Actuator ofthis invention, allows for mechanical energy production, and can operateunder stress conditions. In one embodiment, the volumetric ordimensional change occurs against an applied stress such that mechanicalwork is conducted, where the mechanical work divided by the initialvolume of the actuator (mechanical energy density) exceeds (kJ/m3)values of between 0.1-5000 kJ/m³. In one embodiment, the mechanicalenergy density exceeds 1 kJ/m³, or in another embodiment, the mechanicalenergy density exceeds 10 kJ/m³, or in another embodiment, themechanical energy density exceeds 50 kJ/m³, or in another embodiment,the mechanical energy density exceeds 100 kJ/m³, or in anotherembodiment, the mechanical energy density exceeds 200 kJ/m³, or inanother embodiment, the mechanical energy density exceeds 300 kJ/m³, orin another embodiment, the mechanical energy density exceeds 500 kJ/m³,or in another embodiment, the mechanical energy density exceeds 1000kJ/m³, or in another embodiment, the mechanical energy density exceeds1250 kJ/m³, or in another embodiment, the mechanical energy densityexceeds 1500 kJ/m³, or in another embodiment, the mechanical energydensity exceeds 1750 kJ/m³, or in another embodiment, the mechanicalenergy density exceeds 2000 kJ/m³, or in another embodiment, themechanical energy density exceeds 2250 kJ/m³, or in another embodiment,the mechanical energy density exceeds 2500 kJ/m³, or in anotherembodiment, the mechanical energy density exceeds 2750 kJ/m³, or inanother embodiment, the mechanical energy density exceeds 3000 kJ/m³, orin another embodiment, the mechanical energy density exceeds 3250 kJ/m³,or in another embodiment, the mechanical energy density exceeds 3500kJ/m³, or in another embodiment, the mechanical energy density exceeds3750 kJ/m³, or in another embodiment, the mechanical energy densityexceeds 4000 kJ/m³, or in another embodiment, the mechanical energydensity exceeds 4500 kJ/m³, or in another embodiment, the mechanicalenergy density exceeds 5000 kJ/m³, or any range in between.

In another embodiment, the electrochemical actuators of this inventionhave a volumetric or dimensional change occurring against an appliedstress, such that mechanical work is conducted, wherein the mechanicalwork divided by the mass of the actuator (specific mechanical energy)exceeds between 0.04-2,000 J/g. In one embodiment, the specificmechanical energy exceeds 0.4 J/kg, or in another embodiment, thespecific mechanical energy exceeds 1 J/kg, or in another embodiment, thespecific mechanical energy exceeds 2 J/kg, or in another embodiment, thespecific mechanical energy exceeds 3 J/kg, or in another embodiment, thespecific mechanical energy exceeds 4 J/kg, or in another embodiment, thespecific mechanical energy exceeds 5 J/kg, or in another embodiment, thespecific mechanical energy exceeds 10 J/kg, or in another embodiment,the specific mechanical energy exceeds 20 J/kg, or in anotherembodiment, the specific mechanical energy exceeds 40 J/kg, or inanother embodiment, the specific mechanical energy exceeds 80 J/kg, orin another embodiment, the specific mechanical energy exceeds 100 J/kg,or in another embodiment, the specific mechanical energy exceeds 200J/kg, or in another embodiment, the specific mechanical energy exceeds300 J/kg, or in another embodiment, the specific mechanical energyexceeds 400 J/kg, or in another embodiment, the specific mechanicalenergy exceeds 500 J/kg, or in another embodiment, the specificmechanical energy exceeds 750 J/kg, or in another embodiment, thespecific mechanical energy exceeds 1000 J/kg, or in another embodiment,the specific mechanical energy exceeds 1200 J/kg, or in anotherembodiment, the specific mechanical energy exceeds 1350 J/kg, or inanother embodiment, the specific mechanical energy exceeds 1500 J/kg, orin another embodiment, the specific mechanical energy exceeds 1600 J/kg,or in another embodiment, the specific mechanical energy exceeds 1800J/kg, or in another embodiment, the specific mechanical energy exceeds2000 J/kg.

The actuators of the invention have in some aspects designs orarchitectures providing for improved load bearing, or for load bearingby a single active material of the cell. Such designs can also avoidhaving a porous separator under load as in the laminated designs. Thusin one embodiment, an actuator of this invention may have an electrodecompound or composite electrode providing actuation forming amultiplicity of load-bearing members in the primary direction ordirections of actuation, wherein each member is exposed to anintercalation compound in one or more directions from the primarydirection or directions of actuation. In another embodiment, the membersmay be formed as a pattern of posts or bars or ridges. In anotherembodiment, the actuator design comprises an array of posts wherein onlyone active material is load-bearing. In another embodiment, the actuatordesign is such that when one electrode performs actuation, the otherelectrode is buried in a stiff porous separator, such that it (thelatter) is not load-bearing.

In another embodiment, the lateral dimensions of the members may have atleast one half-thickness that is sufficiently small to allow substantialintercalation of the intercalation compound, during a desired timeperiod of actuation. In another embodiment, the intercalation compoundsource is placed adjacent to a pattern of members or, in anotherembodiment, between members allowing ion insertion from a direction thatis not the primary direction or directions of actuation.

In one embodiment, an electrochemical actuator of this invention willhave a high load-bearing and stress-generating capacity as well as ahigh rate of actuation. The actuation compounds of the invention as wellas composite electrodes incorporating such actuation compounds arecapable of supporting substantial stress in tensile loading, in oneembodiment, and in another embodiment, even greater stress incompressive loading.

For example, a polycrystalline graphite material may have a compressivefailure stress of 100-200 MPa, a highly oriented or single crystalgraphite may have compressive failure stress in the c-axis direction(normal to the graphene planes) in excess of 500 MPa or even in excessof 1 GPa, and a densely sintered metal oxide intercalation compound mayhave compressive failure strength in excess of 400 MPa or even in excessof 1 GPa. In one embodiment, certain applications may require ioninsertion to occur from a direction other than the highly loadeddirections. For example, in the fiber actuators described herein, in oneembodiment, load bearing is primarily along the axis of the fibers,while ion insertion occurs in the transverse direction.

According to this aspect of the invention, and in one embodiment,actuators are designed to allow ion insertion from a transversely orlaterally placed ion source into load-bearing members of an actuatorthat are supporting compressive or tensile load. The lateral ortransverse dimensions of the load-bearing members may be selected on thebasis of ion and electron transport kinetics well-known to those skilledin the art of electrochemical materials and devices.

In one embodiment, where lithium intercalation compounds are used forelectrochemical actuation, the time necessary to lithiate or delithiatea certain cross-section of material to a desired ion concentration andcorresponding strain may be readily determined knowing the rate of iontransport into the material. Such determinations may be readily testedexperimentally or made theoretically using tabulated or estimated valuesof properties such as ion diffusion coefficients, ionic and electronicconductivities, and surface reaction rate coefficients.

Extremely high stresses and energy densities are achievable using asuitably designed actuator and actuating material, as will be understoodby one skilled in the art, and as exemplified herein. In one embodiment,an oriented graphite material is used as a load bearing actuatingmaterial, with the c-axis of the graphite oriented substantially in thedirection of desired actuation. In one embodiment the graphite has amultiplicity of individual elements together bearing the load, each ofwhich has a smallest cross-sectional width that is 200 micrometers orless, allowing substantial ion intercalation over a useful actuationtime. As shown in the Examples, in one such embodiments an actuationstrain of as high as 1.2% is obtained under a stress as high as 100 MPa(one metric ton per cm²), providing an energy density of 1200 kJ/m³, or4.3% is obtained under a stress of 30 MPa, providing an energy densityof 1290 kJ/m³. While these Examples demonstrate the capabilities of thepresent invention for extremely high actuation energy density, it isunderstood that useful mechanical work can be performed according to theinvention while employing much lower strains and actuation energies thanthe ultimate capabilities of a particular actuator.

In another embodiment, the actuator design is such that one or, inanother embodiment, both of the materials forming the electrochemicalcouple, namely the positive and negative electrode materials, may beload bearing material. In some embodiments this is desirable because oneof the materials may expand when the cell is charged or discharged whilethe other contracts. By having the load borne by one active material, alarger net strain and mechanical energy density may be obtained than inthe case where the two materials are joined in series in the directionof loading, and the net strain includes that in both materials. Byplacing the two active materials in a parallel arrangement between theload-bearing surface of the actuator rather than in series, in anotherembodiment, it is also possible to design the actuator such that bothmaterials contribute to mechanical actuation, but in differentproportions or even in different directions (expansion versuscontraction) as the state of charge varies.

In some applications of electrochemical actuators it is advantageous toprovide for rotary motion. In one embodiment, the invention provides aRotational Electrochemical Actuator, comprising rolled layers of annegative electrode, a positive electrode and an intercalating species,wherein the rolled layers assume a laminate configuration, and whereinthe Rotational Electrochemical Actuator is subjected to an appliedvoltage, whereby application of the voltage produces intercalation ofthe intercalating species in the actuator, resulting in a volumetric ordimensional change of the actuator such that the rolled laminateconfiguration winds or unwinds, and torque is produced.

The Rotational Electrochemical Actuator 56 would use, in one embodiment,a design similar to that of the Multilayer Stacked ElectrochemicalActuator, comprising laminates of current collectors 58, which, in oneembodiment, comprise aluminum and copper, negative electrodes 60, whichin another embodiment, comprise carbon, positive electrodes 62, which inanother embodiment comprise an oxide, and a separator 64, which inanother embodiment, may comprise a polymer film (FIG. 39). In anotherembodiment, a structural aluminum layer 66 is added, or in anotherembodiment, the aluminum foil current collector is replaced withstructural aluminum. In another embodiment, the copper layer may bestructural as well. In another embodiment, the RotationalElectrochemical Actuator is infiltrated with electrolyte 68. Theactuator may be assembled as a spiral 70, around an inner mandrel 72,and covered by an outer shell 74. When the system is charged, asignificant volume change (˜5%) would occur, causing the rolled actuatorto unwind. The amount of rotary motion induced would be proportional tothe product of the volume change and the number of turns in the spiral.As a result, a spiral actuator with, say, 20 layers, would be capable ofvery high torques, and significant rotary motion.

In one embodiment, Rotational Electrochemical Actuator winds, orunwinds, in response to application of voltage, or cessation thereof. Inanother embodiment, when the rolled laminate configuration winds orunwinds, rotary motion is produced. In another embodiment, the rotarymotion ranges from 1-360°. In another embodiment, the rotary motionproduces 1 or more rotations, which, in another embodiment, are completeor incomplete. In another embodiment, the rotation is in a clockwisedirection or counter clockwise direction, or a combination thereof.

It is possible that shear strains may be produced in the lamination, asa result of the construction of the Rotational Electrochemical Actuator.In one embodiment, shear strain is mitigated by using a thick polymerseparation layer to allow shearing motions between structural layers. Inone embodiment, selection of the polymer layer includes that of a lowshear modulus in order to allow the shear, but high bulk modulus toensure that the actuation energy in not wasted in the compression of thepolymer layer. In another embodiment, the spiral may be constructed withan additional elastomeric layer to achieve this result.

In some applications of the electrochemical actuators of the invention,it is advantageous to provide for actuation in one or more directionswithin a plane, or to have the actuator exert a tensile stress. In oneembodiment, the invention provides a Continuous Fiber ElectrochemicalActuator, comprising a fibrous negative electrode, a positive electrodeand an intercalating species wherein the Continuous FiberElectrochemical Actuator is subjected to an applied voltage, wherebyapplication of the voltage or its cessation induces intercalation of theintercalating species in the actuator, resulting in a volumetric ordimensional change of the actuator, such that said fibrous negativeelectrode undergoes elongation. By “continuous fiber” it is understoodthat the fibers comprising the active material have an aspect ratio ofat least 10 to 1 and preferably greater than 20 to 1, and are loadbearing along the axis of the fibers. In one embodiment a majority ofthe fibers continuously span an actuator device comprising at least apositive electrode and negative electrode and electrolyte.

In one embodiment, the Continuous Fiber Electrochemical Actuator 76 iscomprised of a fiber composite system, similar to graphite fibercomposites, in which the active fibers form the negative electrode 78,which, in one embodiment are carbon fibers, and undergo significantelongation under intercalation. (FIG. 40). In one embodiment, disorderedcarbon fibers are utilized, which, in another embodiment, expandisotropically upon lithium intercalation. The fiber negative electrodemay be separated from the positive electrode 80, which in oneembodiment, is a lithium-source positive electrode, by a polymer orinorganic separator 82, and a liquid or solid electrolyte layer 84.Current collectors 86 and 88, respectively, may be connected to thepower source 90 in the actuator.

In one embodiment, the carbon fibers are the primary structural layer,and are anchored at each end to form a completed actuator. In oneembodiment, the Continuous Fiber Electrochemical Actuator can actuate intension as well as in compression.

In another embodiment, the actuator 92 is comprised of individualnegative electrode fibers 94, such as carbon, are coated with a ceramicor polymer electrolyte 96 and a lithiated positive electrode 98,connected to a power supply 100 as shown in FIG. 41. These fibers couldthen be used to form, in one embodiment, an active fiber composite 102,which, in another embodiment, uses a conventional matrix (such asepoxy), found, in another embodiment, in graphite-reinforced plasticcomposites. Masking the ends of the fibers during the coating processwould produce step layers, as shown in the figure, allows, in anotherembodiment, the electrical connections to be applied to the ends of thefibers.

In another embodiment, the Continuous Fiber Electrochemical Actuator iscomprised of multiple coated fibers, which are utilized to form a fibercomposite. In another embodiment, the composite further comprises amatrix, which, in another embodiment, is a polymer. In anotherembodiment, the composite of the Continuous Fiber ElectrochemicalActuator comprises fiber ends, which are uncoated. In anotherembodiment, the uncoated ends of the fibers enable electricalconnections to be applied to the ends of the fibers.

In another embodiment, the Continuous Fiber Electrochemical Actuatorprimarily actuates in tension. For example, graphite can be lithiated upto a composition LiC₆ with an accompanying volume expansion of 13.1%,and disordered (isotropic) carbons can be lithiated to still higherconcentrations and expansions. A carbon fiber can, according to thisaspect of the invention, exhibit axial displacement of about 5%, whilepossessing a high elastic modulus (>500 GPa for commercially availabledisordered-carbon fibers).

In another embodiment, the Continuous Fiber Electrochemical Actuatorcomprises multiple layers, which, in another embodiment are assembled inparallel or in perpendicular orientation. In another embodiment, theperpendicular orientation allows positive and negative shearingactuation of the actuator, which, in another embodiment, producestorque, or, in another embodiment, produces rotation. In anotherembodiment, the perpendicular orientation allows for charge transferbetween layers when low voltage is applied.

In another embodiment, the Continuous Fiber Electrochemical Actuatorcomprising multiple layers, wherein a layer of carbon fibers is addedwith orientation perpendicular to a first layer. According to thisaspect, both positive and negative shearing actuation results, producingan actuator capable of twisting an object, such as, in one embodiment, awing or in another embodiment a blade in both positive and negativedirections. In another embodiment, such an orientation reduces the totalpower requirements, by allowing charge to be transferred back and forthbetween layers at a low voltage. In another embodiment, such anactuation system might be capable of 3% elongation in the fiberdirection. In another embodiment, the Continuous Fiber ElectrochemicalActuator can be constructed as a pack, similar in form factor to activefiber composite (AFC) packs based on piezoelectric fibers, which couldbe used to actuate a blade or wing, producing significant actuated twistcapability (See FIG. 41).

In one embodiment, the invention comprises actuators that can deamplifystrain, and thereby amplify stress. In one embodiment, depicted in FIG.30, a woven actuator is provided in which a transverse (orthrough-thickness) displacement of one or more electrochemical actuatorsis converted into a longitudinal or in-plane displacement with a straindeamplification factor that is determined by the respective dimensionsof the actuator. The design features, construction, and testing of thisactuator type is exemplified in Example 9. Such actuators are useful innumerous applications including shape-morphing or beam-bendingapplications where a relatively thin actuator, for example onesufficiently thin to use in the skin or shell of a fuselage, rotor,wing, watercraft hull, or land vehicle body is desired.

In one embodiment, the woven structure comprises metallic wires, or inanother embodiment, a composite material, or a combination thereof. Inone embodiment, the composite material comprises graphite fibers, or inanother embodiment, fiberglass fibers in a matrix. In one embodiment,“matrix” refers to any matrix known in the art, and may comprise, forexample, an epoxy, or in another embodiment, two-part epoxies,temperature cured epoxies, thermoplastics, etc. In one embodiment, arubberizing agent (see Crawley, E. F. and Ducharme, E. H. ASME,International Gas Turbine Conference and Exhibition, 32nd, Anaheim,Calif.; UNITED STATES; 31 May-4 Jun. 1987. 11 pp. 1987) may be used tolower the matrix modulus, to increase the flexibility of the mechanism.

In another embodiment, the amplifying mechanism is a composite structureformed not by interweaving fibers, but by fibers running roughlyparallel on the top and bottom sides of one of more electrochemicalactuators, with the fibers on opposite sides stitched or sewn togetheron the left and right of each EC actuator.

The high strain of the present electrochemical actuatorsnotwithstanding, many applications benefit from an amplification ofstrain, which for energy conservation necessitates a deamplification ofstress. In another embodiment, the invention comprises actuators thatamplify strain. In one specific embodiment shown in FIG. 29, theactuation strain of an electrochemical actuator element or series ofactuator elements, here a stack of multilayer actuator devices, isamplified by an assembly incorporating a lever and a fulcrum that alsoserves as a flexure. In one embodiment the housing for the actuatingelements or the lever and fulcrum are formed from one piece of material,for example from an electro-discharge machined piece of a metal or froma formed single body of a polymer or reinforced polymer composite,providing for a compact and economical design. Such actuators may beused singly or multiply as positioners, latches, lifters, or to changethe shape of a structure. While actuators having a lever and fulcrumpowered by piezoelectric elements are known, for example the commercialproducts manufactured by Physik Instrumente, the present actuators havea much larger range of motion as shown in Example 8.

In another embodiment, this invention provides a method of actuation,comprising the step of applying a voltage to an actuator of thisinvention, comprising an negative electrode, a positive electrode and anintercalating species, wherein applying voltage causes current flowinducing intercalation of the intercalating species in the actuator,whereby intercalation induces a volumetric or dimensional change of anactuator of this invention. The amount of actuation is in one embodimentcontrolled by controlling the voltage, and in another embodiment bycontrolling the total amount of current flowing into the device.

It is to be understood that all the embodiments for the actuators ofthis invention listed herein, are applicable to methods of actuationusing the same, and are to be considered as part of this invention.

In another embodiment, this invention provides a method of producingtorque or rotary motion in a structure or an apparatus comprising aRotational Electrochemical Actuator, comprising the step of applyingelectric current to a Rotational Electrochemical Actuator comprising annegative electrode, a positive electrode and an intercalating species,wherein applying current induces intercalation of the intercalatingspecies in the actuator resulting in a volumetric or dimensional changeof the actuator such that said rolled laminate layers unwind, and torqueor rotary motion is produced.

In another embodiment, this invention provides a structure or apparatuscomprising an actuator of this invention. In one embodiment, thestructure or apparatus is adaptive. In another embodiment, the actuatoris used as an element to apply stress at a site on the structure orapparatus that is distal to the actuator. In another embodiment, thestructure or apparatus amplifies the volumetric or dimensional changeinduced by the actuator.

In one embodiment the adaptive structure or apparatus 104 comprises anelectrochemical actuator of this invention 106, mounted on its surface108 (FIG. 42A).

In one embodiment, a structure such as a beam or plate or any structureof a size ranging from the MEMS scale to, in another embodiment, a largescale structure can be actuated with a surface mounted electrochemicalactuator of this invention. In one embodiment, the electrochemicalactuators of this invention are designed to produce in-plane deformationor actuation stress. In one embodiment, the deformation produced viaplanar thin film electrochemical actuators of this invention is normalto the plane of the surface where the actuator is positioned. In oneembodiment, deformation in such an orientation is least constrained andconstruction of the actuator or, in another embodiment, its integrationwithin a structure or apparatus is so designed as to produce a highstress or deformation in the plane of the surface.

In one embodiment, the actuators of this invention may produce blockedstresses of between 0.1-1000 MPa. In another embodiment, the actuatorsof this invention may produce blocked stresses of between 0.1-10 Mpa,or, in another embodiment, actuators of this invention may produceblocked stresses of between 0.1-100 Mpa, or, in another embodiment,actuators of this invention may produce blocked stresses of between 1-10MPa, or, in another embodiment, actuators of this invention may produceblocked stresses of between 1-100 MPa, or, in another embodiment,actuators of this invention may produce blocked stresses of between1-1000 MPa, or, in another embodiment, actuators of this invention mayproduce blocked stresses of between 10-100 MPa, or, in anotherembodiment, actuators of this invention may produce blocked stresses ofbetween 10-1000 MPa, or, in another embodiment, actuators of thisinvention may produce blocked stresses of between 100-1000 MPa.

In one embodiment, multiple actuators are distributed in an apparatus.In one embodiment, the distributed electrochemical actuator technologyof this invention is capable of imparting multiple degrees of freedom toactive structures comprising the actuators.

In one embodiment, integration of an actuator within a structure orapparatus 110 is as schematically depicted in FIG. 42B. Theelectrochemical actuator, or in another embodiment, actuators 140, arein one embodiment, thin film, or in another embodiment, thick filmlaminated electrochemical actuators, which are oriented normally to thesurface, and are positioned within a stiff surface layer 120, on asubstrate 130.

The positioning and design of the actuators may result in a greaterdeformation produced in the surface plane, via, in one embodiment,changing the aspect ratio of the expanding and contracting elements(FIG. 42C), the positive electrode 150 and negative electrode 160. Sucha construction as depicted in the figure produces a large, in-plane, netdeformation upon charging/discharging of the actuator, evident whenviewed looking down the plane of the surface (C), or in cross-section(D).

In another embodiment, the laminated electrochemical actuator itselfundergo deformation. In one embodiment, the deformation is a bending ofthe actuator itself, as a result of expansion of one electrodeconcurrent with contraction of another, during the same charge ordischarge cycle. For example, and in one embodiment, an negativeelectrode comprising carbon will expand, as carbon expands whenlithiated and a positive electrode comprising LiCoO₂ expands whendelithiated, resulting in a partial compensation of any deformation ofthe actuator comprising the two.

In another embodiment, an actuator 170 comprising a carbon or lithiumnegative electrode 200, which expands when lithiated, and a LiMn₂O₄ orLiFePO₄ positive electrode 190, which contracts when de-lithiated, ifbonded to a separator 180, will produce a marked bend in the entirestructure (FIG. 43 A).

In another embodiment, a laminated electrochemical actuator of thin filmor thick film design of this invention, wherein a volume change in bothnegative electrode and positive electrode is being utilizedsimultaneously, will position electrodes yielding maximum expansion, inone embodiment, the negative electrode, facing outward from a surfacethat is intended to be deformed from lesser to greater convexity. In oneembodiment, an airfoil 210 would be designed to comprise actuatorsassuming such a configuration. According to this aspect, the actuatorwould be positioned, such that the negative electrode is facing outward230, from the surface of the apparatus 220, such that followingactuation, a greater curvature outward occurs. In one embodiment, such aconfiguration enables the device to be discharged in the relaxed state.

In another embodiment, electrochemical actuation may be performed usinga supporting material such as a substrate as the electro-active materialitself (FIG. 43C). According to this aspect of the invention, and in oneembodiment, the structure comprising the actuator 240, comprises asilicon wafer 250 that can be lithiated from the surface 270, via thelithium metal or lithiated oxide electrode as the lithium source, inorder to induce volumetric expansion hence bending. In one embodiment,other metalloids, or, in another embodiment, metals (e.g. Al whichlithiates to LiAl) or, in another embodiment, oxides may be usedsimilarly.

In another embodiment, a structure or apparatus 280 may be made to bendaround more than one axial direction, such as, in another embodiment, totwist and curve concurrently, by having an array of electrochemicalactuators 300 on the surface of the structure or apparatus 290 andactuating them non-uniformly in a prescribed manner (FIG. 44).

In one embodiment, the structure or apparatus will twist about thex-axis and bend about the y-axis, if individual actuators are actuatedappropriately to produce this result. According to this aspect of theinvention, and in one embodiment, if there is a net expansion induced onthe surface, then the surface will bend, as a whole in response, and, inanother embodiment, if different degrees of bending are induced locallyas one progresses down the x-axis, then overall, there will be atwisting along this axis.

In another embodiment, according to this aspect of the invention, thestructure or apparatus may comprise a series of small actuators sodesigned as to produce an overall twist in the structure comprising theactuators, wherein the structure may be quite large, and the twistingexerted despite high frictional and other resistance forces exerted onthe structure. For example, and in one embodiment, a series ofMultilayer Stacked Electrochemical Actuators with an aspect ratio of, inone embodiment, 1, or in another embodiment, 0.5, or in anotherembodiment, 2.0, or in another embodiment, 1.5, or in anotherembodiment, between 0.5 to 2, is placed on a substrate, at an angle tothe leading edge of the substrate. In one embodiment, the MultilayerStacked Electrochemical Actuator is in the shape of a cube, or inanother embodiment, in the shape of a cylinder. In another embodiment,the Multilayer Stacked Electrochemical Actuators range in size between0.5 to 10 cm, or in another embodiment, between 0.5 to 5 cm, or inanother embodiment, 1 to 3 cm.

In another embodiment, the substrate is a wing of an aircraft 330, andthe actuators of this invention 320 arranged according to this aspect ofthe invention are used to twist the wing (FIG. 45). In anotherembodiment, the actuators may be utilized to raise and lower flapspositioned on a wing, for greater flight control. In another embodiment,the actuators of this invention may be utilized to reversibly unfurl awing (FIG. 44 B).

According to this aspect of the invention, and in other embodiments, theactuators may be utilized for unfurling a fin or wing on a missile oraircraft. In one embodiment, large strains produced by electrochemicalactuation enable the morphing of surfaces. By the term “morphing”, it ismeant, in one embodiment, to refer to an overall change in structure. Inone embodiment, an otherwise rigid wing or fin may be furled when thevehicle is stored, and unfurled when the vehicle is deployed, via theelectrochemical actuators of this invention. In another embodiment,significant change in wing sweep is achieved, which, in anotherembodiment, enables a vehicle comprising the electrochemical actuatorsof this invention to have both subsonic and supersonic capabilities.

In one embodiment, the structure or apparatus moves in or beyond theatmosphere. In one embodiment, such a structure or apparatus may be anaircraft, a missile, a spacecraft or a satellite. In another embodiment,such a structure or apparatus may be part of an aircraft, a missile, aspacecraft, a worm, a robot or a satellite. In other embodiments, thepart may be a wing, a blade, a canard, a fuselage, a tail, an aileron, arudder, an elevator, a flap, a pipe, a propellor, a mirror, an opticalelement, or a combination thereof. In other embodiments, the part may bean engine, a motor, a valve, a regulator, a pump, a flow control device,a rotor, or a combination thereof.

In another embodiment, the structure or apparatus moves in water. In oneembodiment, such a structure or apparatus may be a boat, a ship, asubmarine or a torpedo. In another embodiment, the structure orapparatus is a part of a boat, a ship, a submarine or a torpedo. Inanother embodiment, the part is a blade, a rudder, a pipe, a propellor,an optical element, or a combination thereof. In another embodiment, thepart is an engine, a motor, a valve, a regulator, a pump, a flow controldevice, a rotor, a switch or a combination thereof.

In another embodiment, the structure or apparatus is a a bomb, a meansof transportation, an imaging device, a robotic, a worm, a prosthesis,an exoskeleton, an implant, a stent, a valve, an artificial organ, an invivo delivery system, or a means of in vivo signal propagation.

For example, and in an embodiment of this invention, high-authoritycontrol of helicopter rotor blades may be accomplished via the use of anactuator of this invention. The actuators of this invention may beutilized, in one embodiment of the invention, for producinghigh-authority, low-bandwidth control required to allow auto-rotation,or to improve hover performance at hover levels in aircraft. In oneembodiment, a Rotational Electrochemical Actuator of this invention willproduce a 10 degree tip rotation, or more, which may be used in hoverapplications, which typically require 8-15 degrees of authority. Inanother embodiment, a Rotational Electrochemical Actuator of thisinvention will provide an electric, swashplateless rotor for use inhover application.

In another embodiment, single bi-layer or stack actuators comprising arigid porous separator, or a solid electrolyte can be used, whichprovides high stiffness to the actuator. A series of such actuatorelements may be patterned on a substrate, including on silicon glass, oraluminium oxide, or some other such substrate of high stiffness, andused for high force actuation, for production of a nastic structure. Inone embodiment, the term nastic structure refers to a structure, whichdeforms in response to a stimulus. According to this aspect of theinvention, a series of actuators may be placed on a substrate which whenactivated, creates a deformation, in another embodiment, in an overallstructure comprising the actuators.

In one embodiment, devices that utilize the technology of this inventioncomprise motors, such as, in one embodiment, a linear, or, in anotherembodiment, a rotational motor. In another embodiment, the device is apump, such as, in another embodiment, a microhydraulic pump, or inanother embodiment, a microfluidic pump. In another embodiment, thedevice is a mirror array, or in another embodiment, an optical elementused for optical switching. In another embodiment, the device is aphotonic device where actuation induces a change in an optical path orproperties. In another embodiment, the device is a worm or robot thatmoves as a result of actuation, moving, in another embodiment, a seriesof elements in a given sequence.

The energy density of electrochemical actuators (ECAs) may be quitehigh, and the choice of materials will influence the resulting energydensities obtained, with, in another embodiment, the advantage of easierdistribution of ECAs throughout a morphing aircraft structure, or, inanother embodiment, their production as small units that can be gangedto produce high authority at a single point or distributed widely over astructure to produce localized control. In another embodiment, astructure comprising the ECAs may be able to “morph” in many degrees offreedom, and achieve high performance over a wide range of conditions.In one embodiment, such an application is exploited in constructingparts of an airplane. For example, in one embodiment, one might developa wing with distributed ECAs that would allow high levels of twist (5deg or more) which allow the elimination of ailerons, or, in anotherembodiment, significant sweep changes (20 deg or more) to allow goodperformance at both subsonic and supersonic speeds, or, in anotherembodiment, airfoil shape changes (camber and thickness) large enough tooptimize wing performance over Mach numbers ranging from low subsonic tosupersonic speeds.

In another embodiment, this invention provides a pump comprising atleast one electrochemical actuator, comprising an negative electrode, apositive electrode, an intercalating species, and at least one valve,wherein following application of a voltage causing current flow in theactuator, intercalation of the intercalating species produces a changein volume in the actuator, such that fluid is directed through thevalve. In one embodiment, the pump comprises a series of actuators. Inanother embodiment, the actuators may be placed in a parallel series. Inanother embodiment, the actuators may be placed in a plane of a surfaceso as to direct fluid through designed channels.

In one embodiment, a microfluidic pump may be designed, using anelectrochemical actuator of this invention, wherein the actuatorproduces a net volume charge upon charging and discharging (FIG. 46).According to this aspect of the invention, and in one embodiment, themicrofluidic pump 340, comprises a positive electrode 350, and negativeelectrode 360, separated by an electrolyte layer 370, which according tothis aspect of the invention is a liquid electrolyte. In one embodiment,the electrolyte may itself be the working fluid of the pump, or inanother embodiment, the working fluid may be a separate fluid from theelectrochemical actuator system. In another embodiment, the actuatorundergoes a net volume change upon charging and discharging, followingthe application of voltage 390, or its cessation, respectively, whichenables fluid propulsion through the valves 380.

Volume changes that may be achieved, such as those exemplified inExample 3 herein, may range, in one embodiment, from 1 to 10%, or, inanother embodiment, from 5 to 10%, or, in another embodiment, from 10 to15%, or, in another embodiment, from 15 to 20%, or, in anotherembodiment, from 5 to 10%, or, in another embodiment, from 5 to 10%, or,in another embodiment, from 20 to 25%, or, in another embodiment, from25 to 30%, or, in another embodiment, from 30 to 35%, or, in anotherembodiment, from 35 to 40%, or, in another embodiment, from 40 to 45%,or, in another embodiment, from 45 to 50%, or any range as describedherein.

In one embodiment, an assembly of actuators can be used to create afluid or gas pump or a microfluidic device. In one embodiment, a seriesof actuators may be assembled in a plane, wherein actuation produces anet flow of fluid though channels, whose shape is controlled by theactuator design and positioning within the plane (FIG. 46B). In oneembodiment, the pump or microfluidic device 400 comprises a series ofactuators 410, which upon charging and discharging induce volumechanges, which can, in one embodiment, direct fluid flow from intake420, through exit 420 of the device, through channels whose shape may becontrolled, in another embodiment, via specific actuator design, whichmay comprise assembly on a substrate 430. In one embodiment, operationof the actuators in a series propels the fluid through the device. Inanother embodiment, positioning of the actuators is such that channelsare designed, as depicted in FIG. 46C. Such actuators can be, in oneembodiment, of single bi-layer, or, in another embodiment, of stackeddesign. In one embodiment, the device will comprise a high moleculestack for the actuators. According to this aspect of the invention, andin one embodiment, a rigid porous separator or, in another embodiment, asolid electrolyte can be used, such as, in another embodiment, a LIPONelectrolyte. In another embodiment, the stacked actuators may comprisethin film batteries in an array on a substrate, in a single bi-layer(single electrochemical cell) or multilayer stack sequence. In oneembodiment, the substrate on which the actuators are patterned maycomprise silicon glass, aluminium oxide, or any substrate of highstiffness, and may, in another embodiment, be used for high forceactuation, or, in another embodiment, in microfluidic devices for fluidpropulsion. In another embodiment, according to this aspect of theinvention, a nastic structure is thus designed, in which a series of gasor liquid filled chambers are actuated so as to create deformation ofthe overall structure.

In another embodiment, actuation is via a fluidic system, whichcomprises an electrolytic membrane, which pumps an ion from one side toanother, producing a liquid rather than a gas in the process, asexemplified herein in Example 4 and FIG. 15. By pumping a liquid, muchhigher actuation forces can be produced since liquids have much lowercompressibility. Actuators of this kind can be used, in one embodiment,in fluidic, or in another embodiment, in micro fluidic devices, or, inanother embodiment, in micro hydraulic devices, or in anotherembodiment, in nastic structures or, in another embodiment, incompressing cellular micro-fluidic or, in another embodiment, in microhydraulic devices.

In one embodiment, such an electrochemical actuator, will comprise annegative electrode, a positive electrode and an electrolytic membraneand an ion, wherein application of voltage to the electrochemicalactuator or its cessation induces pumping of the ion from one side ofthe membrane to the other side, resulting in the generation of a liquid,thereby producing a volumetric or dimensional change in the actuator. Inone embodiment, the ion is a proton (H+). In another embodiment, theliquid comprises H₂O₂, or in another embodiment, the liquid comprisesH₂O.

In another embodiment, this invention provides a morphing plate, or inanother embodiment, morphing beam architecture comprising the actuatorsof this invention. According to this aspect of the invention, and in oneembodiment, a plate architecture containing distributed electrochemicalactuators is provided, which may yield, in another embodiment, amultiple shape target (FIG. 47). In one embodiment, the plate maycomprise three orientations of in-plane, independently-addressableactuators, such as, for example, 0°, +60°, −60°, as illustrated by thered-green-blue motif in FIG. 48A. This hexagonal network does notnecessarily represent actual physical cell walls or boundaries (althoughsuch an assembly represents one embodiment of this invention), but may,in another embodiment, describe a distribution of “unit cells”, eachacted upon by a single actuator of a given orientation. Many degrees ofmorphing freedom are possible in a plate, in another embodiment, asschematized in FIG. 48B, in which the surfaces contain such arrays ofembedded addressable actuators.

In one embodiment, the construction in FIG. 48B may, for example, be a10×10 array of actuators embedded in each side of a monolithic platemade of a polymer or structural metal, or a composite plate. Shapechanges could be induced, in one embodiment, as follows:

If all actuators are simultaneously charged (discharged) so that theyexpand (contract), the plate will expand (contract) biaxially. Accordingto this aspect of the invention, there may be a lesser extent ofthickness expansion (contraction), determined primarily by the expansionanisotropy designed into the multilayer actuator. The net macroscopicexpansion of the plate depends, according to this aspect, and in oneembodiment, on the area or volume fraction of actuators and details ofload transfer. The actuator fraction may be, in one embodiment, 50% ormore, so that an actuator exhibiting 10% volume expansion results in a5% expansion of the plate.

In one embodiment, the lengthening, shortening, shear, or combinationthereof, of the plate along any direction in the plane of the plate maybe accomplished by actuating the three orientations non-uniformly.

In another embodiment, curvature about any axis or axes may be producedby actuating the two sides of a plate in a non-uniform manner. Forexample, if all actuators on one surface are expanded equally, whilethose on the opposing surface either contract equally or are notactivated, the plate will cup in a uniform (macroscopically spherical)curvature. The net curvature may depend, in another embodiment, on thestrain induced at each surface, the thickness of the plate orcombination thereof; for example, a 2 cm thick plate having +5%expansion at one surface and −5% contraction at the other may exhibit aradius of curvature of 20 cm.

In another embodiment, twisting, saddle curvatures, or more complextopologies may be produced by actuating the two sides of a plateappropriately, which, in another embodiment, may manifest in thedepicted shape changes as shown in FIG. 47.

In another embodiment, the Continuous Fiber Electrochemical Actuator maybe arrayed such that it is applied to the surface of a plate, in oneembodiment, along the 3 orientations herein described, and actuated toprovide multiple morphing capability (FIG. 48C).

In another embodiment, a combination of stacked and fiber actuators maybe used. Higher morphing performance may be achieved, in anotherembodiment, by increasing the actuator density within the plate. Inanother embodiment, the array may be constructed such that eachhexagonal cell is virtually filled by actuator, for example, as depictedin FIG. 48D. To impart greater thickness expansion or contractioncapability (including varying thickness changes along the plate), thecross-section of the plate may, in another embodiment, also containstacked actuators (for example, as depicted in 48D, panel 2).

It is to be understood that the present invention encompasses anyembodiment, or combinations of embodiments for what is to be consideredan electrochemical actuator of this invention, and the inventionincludes any structure, fabric, device, etc. comprising the same, ormultiples thereof. It is to be understood that several actuators may beincorporated within a single structure, apparatus, device, fabric, thatthe actuators may differ, in terms of their type, materials used toconstruct the actuator, actuation energy provided, preconditioning,stress amplification, or strain amplification properties, etc., and areencompassed by the present invention.

While only a few embodiments of the present invention have been shownand described, it will be apparent to those persons skilled in the artthat many changes and modifications may be made thereunto withoutdeparting from the spirit and scope of the invention, and numerousapplications of the methods and devices of the invention are apparent,and to be considered as part of this invention.

The following examples are presented in order to more fully illustratethe preferred embodiments of the invention. They should, in no way beconstrued, however, as limiting the broad scope of the invention.

EXAMPLES Example 1 Electrochemical Actuator Utilizing LiFePO₄-BasedElectrode and Porous Ceramic Separator

FIG. 1, from Yamada [J. Electrochem. Soc., 148, A224 (2001)] shows thevolume changes that occur in the olivine structure compound (Fe,Mn)PO₄as it is lithiated to the end-member composition Li(Fe,Mn)PO₄. Betweenthe fully lithiated (upper curve) and fully delithiated (lower curve)limits of composition, a volume change of 7.4-10% (linear strain of2.4-3.2%) is realizable depending on the Fe/Mn ratio. FIG. 4 illustratesa design of electrochemical actuator in which a positive electrode isused with a porous alumina separator of high stiffness and load bearingability. The negative electrode comprises Li metal, which is depositedwithin the pores of the porous load-bearing actuator so that it is notload bearing, while still providing a source and sink for Li ions duringthe operation of the actuator. An actuator of this design wasconstructed using a positive electrode for a rechargeable lithiumbattery having a 100 μm thick composite layer comprising anLiFePO₄-based cathode active powder, polymer binder, and carbonconductive additive, deposited on an aluminum foil current collector ofabout 15 micrometer thickness. The electrode had an area of about 1 cm².A 2 mm thick porous alumina separator was used, sectioned from aglass-bonded alumina abrasive product (Norton Company, Worcester,Mass.). On the negative electrode side of this separator, a small amountof Li metal was mechanically squeezed into the pores of the separator,and a copper foil negative current collector was applied. The assemblywas infiltrated with a liquid electrolyte used for lithium rechargeablecells (LP40), sealed in a polymer envelope, and subjected to 1 MPauniaxial prestress applied normal to the layers of the actuator. Theactuator was cycled over a voltage range of 2.0-4.0V at a constant 0.2mA current. The actuator required 8 charge/discharge cycles for thelayers to adjust, and on the 9^(th) cycle, the expected expansion upondischarge was seen as Li+ ws intercalated into the LiFePO₄ positiveelectrode, FIG. 1B, with 2.3% linear strain being observed, in goodagreement with the expected value.

In another example, a 200 mm thick layer (typical for batteryelectrodes) of the electrochemical insertion compound in FIG. 1, whenformulated as a powder-based composite electrode, will have a Young'smodulus of Y=50 GPa (reduced from the single crystal value of ˜150 GPa).Under 3.3V applied voltage this electrode can be fully intercalated toreach a linear strain of ε˜1.5%, thereby generating e³³⁼3.8×10⁴ C/m².The strain energy density (FIG. 4), taken as ½Yε²/ρ where ρ is thematerial density, is estimated at ˜2050 J/kg (5.6×10⁶ J/m3) for theactive material layer, and ˜1000 J/kg (2.8×10⁶ J/m³) for an actuatorstack containing one-half by weight or volume of inactive supportinglayers. For a stack volumetric strain energy density of 2.8×10⁶ J/m³, at1.5% linear strain the equivalent blocked stress should be ˜375 MPa.

Example 2 Multilayer Stacked Actuator Using LiCoO₂ and Carbon as ActiveMaterials

In FIG. 1C, actuation is shown in a multilayer stacked actuator in whichthe positive electrode is LiCoO2 and the negative electrode is carbon.These devices are commercially available batteries fabricated accordingto the “Bellcore” gel-electrolyte technology in which positive electrodeand negative electrode layers (about 30 layers total) are bondedtogether with a bondable separator film, following which the multilayerstack is packaged in polymer. Typical cells are shown in FIG. 2. Thelaminates are oriented normal to the plane of the cell. This battery iselastically soft due to the materials used; it is a relatively lowenergy density device containing a large fraction of soft polymercomponents to facilitate manufacturing. The cells were tested in theas-received state with no preconditioning prior to electromechanicaltesting. The cells were tested in an apparatus designed to apply aconstant pre-stress between two parallel-faced rams while the cells werecharged and discharged. The deformation of the cells in the direction ofapplied stress was measured with a precision displacement transducer.Under 1 MPa applied pressure, a reversible 1% linear expansion wasmeasured, as shown in FIG. 1C, providing for an energy density of 10kJ/m³.

FIG. 3 shows results for a cell under various values of pre-stress from1 MPa to 5 MPa. For this cell the strain is −0.7% at 1 MPa, anddecreases as the pre-stress is increased. In the as-received condition,the cells have a Young's modulus measured in the direction of actuation(normal to the face of the cells and the planar electrode layers) of −30MPa. The maximum actuation energy density in this device is ˜12 kJ/m³.FIG. 4 shows results from a cell that exhibited higher energy density.In this instance the applied pre-stress is 3.5 MPa, and the strainexhibited by the cell is ˜1%, yielding a mechanical energy density of˜35 kJ/m³. This actuation energy density is approximately one-half thatof a typical well-engineered PZT piezoelectric actuator.

Example 3 Multilayer Stacked Actuators and Preconditioning for ImprovedPerformance

Multilayer stacked actuators can have several different internalconstructions, as exemplified in the following. FIG. 5 shows severallithium ion rechargeable cells based on LiCoO₂-carbon chemistry, each ofwhich has a different internal construction. Each of these designs wasdemonstrated to be capable of performing substantial mechanical work,and furthermore, to have improved performance after preconditioningtreatments described herein.

Several samples of each cell were double-vacuum-bagged in plastic andplaced in an isostatic press, and the pressure raised to 45,000 psi andheld for 5 minutes. After testing, the open circuit voltage of the cellswas measured, and all cells were found to have survived the pressuretreatment without suffering an internal short. The capacity of thebatteries changed only slightly after the isopressing treatment, showinga reduction in capacity measured between 3.0 and 4.2V at a C/5 or C/2.5rate of <3% for the 120 mAh and 150 mAh cells, and ˜8% for the 200 mAhcells. A significant volume reduction was seen for each cell. FIG. 6 isa plot of the volume reduction for 10 cells of one type, in which volumereductions ranging from 3.45% to 10.25% were observed. An excess volumein the cell may exist, which can be reduced by the pressing treatment.FIG. 6 also tabulates the macroscopic densities measured by theArchimedes method of each cell type before and after isopressing. Theaverage volume reduction ranges from 1.4% to 5.4%. It is also seen thatthe density of the actuators is low, from 2.15 to 2.39 g/cm³, which maybe compared to the density of a PZT piezoelectric actuator ofapproximately 7.5 g/cm³.

These multilayer cells were found to exhibit viscoelastic deformationunder a uniaxial stress applied normal to the largest face of theprismatic cell, which is normal to the plane of the electrode in thestacked cases. Both as-received and cells exhibited viscoelasticrelaxation. FIG. 7 shows the relaxation in applied stress over time whena cell is subjected to 10 MPa stress in an Instron test machine. Thestress is ramped to 10 MPa at a crosshead speed of 0.002 in/min, andthen the crosshead is stopped so that no further displacement occurs.Over time, the stress then relaxes substantially. However, with eachsuccessive stressing and relaxation cycle, the amount of stressrelaxation decreases, and eventually the cell is able to sustain nearlythe full applied pressure of 10 MPa. Furthermore, the thickness of thecells increased after the stress was removed at the end of the test, andincreased by 2.5 to 4% over a period of several hours. These resultsshow that multilayer stacked actuators of such design using powdercomposite electrodes, microporous polymer separators, and polymerpackaging exhibit visoelastic relaxation properties, but that thedimensions of the cells can be stabilized by applying stress over anextended time prior to using them as electrochemical actuators.

Under uniaxial applied stress, these cells were found to be able towithstand extremely high applied stresses before internalshort-circuiting. Using the Instron apparatus, stress was increased at aconstant crosshead speed while the cell voltage (at a 3.8 Vstate ofcharge initially) was continuously monitored. For the 120 mAh, 150 mAh,and 200 mAh cells respectively, the voltage did not decrease untilpressures of 37 MPa, 57 MPa, and 67 MPa respectively were reached. Thuselectrochemical actuators of these designs may be expected to betolerant to high and abusive stress conditions.

The apparent Young's modulus was measured on these cells in thedirection normal to the largest area faces after the isopressingtreatments. The cells showed two characteristic slopes in thestress-strain relationship, a lower slope between zero and 5 MPaexhibiting a modulus of 50-60 MPa, and a higher slope above 10 MPaexhibiting a modulus of 220-320 MPa. Clearly, a more compressiblecomponent or components of the cells provide for the lower stiffness,which after compression transfers load to higher modulus constituents.It is also shown that even the lower modulus value is greater than themodulus of ˜30 MPa measured in as-received cells prior topreconditioning, thereby demonstrating a benefit of the preconditioningtreatment. These results show that there exist regimes of lower andhigher stiffness for the multilayer stacked actuators, in which theaccessible actuation energy densities may accordingly vary.

The volume expansion of the cells was precisely measured in a fluiddisplacement apparatus. FIG. 8 shows the reversible volumetric expansionof ˜1.5% that was measured on a 150 mAh cell. Other cells showed similarvalues of reversible volume expansion. Thus, these measurements show thecapability of electrochemical actuators to perform volume expansionmechanical work as described in multiple embodiments of the presentinvention. These test results also show that for a multilayer stackedactuator, the expansion is anisotropic, since the volumetric expansionis less than the linear expansion described below. Anisotropic expansionis advantageous for certain applications of electrochemical actuators.

The charge-discharge curves, corresponding strain, and strain energydensity of these multilayer stacked actuators measured after thepreconditioning treatment are shown in FIGS. 9-12. The measurements weremade with an Instron apparatus under conditions where a constant stresswas applied, and the displacement was allowed to vary, with charging anddischarging of the cells at a C/5 rate. In general, a cyclic strainparalleling the charge-discharge cycle is observed, which issuperimposed upon a background creep relaxation as noted earlier. Asshown in FIG. 12, at up to about 10 MPa stress, strains of 1.5% orlarger are readily obtained, and energy densities increase with appliedstress up to 10 MPa, reaching peak values of about 150 kJ/m³. At higherstresses, such as 15 and 20 MPa, actuation strain is diminished but sois the capacity of the cell, indicating that the limiting factor is iontransport rather than the ability of the active material to becharge/discharged under the particular applied stress. It is probablethat the higher applied stresses cause the porosity in the separatorand/or the particle-based electrodes to be decreased, thereby loweringthe rate capability of the cells. Thus, the use of higher modulusseparators and electrode constructions as embodied elsehwhere in thispatent application can allow electrochemical actuation to higherstresses.

Example 4 High Rate Actuation in Multilayer Stacked ElectrochemicalActuators

In order to demonstrate that multilayer stacked actuators can exhibithigh strains and actuation energy densities with rapid rates ofactuation and that substantial actuation performance can be obtainedusing only partial charge and discharge of an electrochemical cell, adifferent actuator was used. The cells tested were commerciallyavailable LiCoO₂-carbon lithium ion cells (Kokam), having a prismaticform factor with dimensions of 59×33.5×5.4 mm³. The cells have a nominalcapacity quoted by the manufacturer of 740 mAh and are rated for up to20 C continuous discharge. They use a microporous polymer separator inan accordion-folded construction alternating layers of the electrodes,as shown for the bottom cell in FIG. 5. An aluminum current collector isused at the positive electrode, and a copper current collector at thenegative electrode. Tests were conducted under a constant 2 MPa uniaxialstress.

These cells exhibit actuation strains of about 2% under a 2 MPa constantstress. The cells were cycled at 2.96 A (4C), 3.70 A (5C), and 4.44 A(6C) for five cycles for a specified amount of time (1 min, 2 min, 5min, 10 min). Between charging and discharging, a 5 minute rest periodwas used to allow the voltage to relax. Before charging, a constantvoltage discharge to 3 V was used to ensure a fully discharged cell,however, a constant voltage hold was not used in the charged statebefore discharging.

FIGS. 13 and 14 show the cyclic actuation strain obtained versus thecycle number, at different values of constant current. At highercurrents, more capacity is achieved in the charge/discharge time, andthe strain increases. In all of the plots, testing conducted using lowercurrent followed by successively higher current. Note that substantialstrains are obtained in very short actuation times, for example at the4.44 A rate (6C) rate, 0.3%, 0.65%, 1.25%, and 1.75% strain are obtainedin 1, 2, 5, and 10 minutes respectively. FIG. 15 shows the chargingactuation strain versus capacity. It is noted that the strain increasesmonotonically with the capacity to which the cell is charged, such thata desired strain level can be selected by charging for a selected time.

In all cases, that discharge capacity (and strain) is less than chargecapacity may be due to differences in the total current passed duringthe charge and discharge cycles under test conditions, and can bereadily adjusted by changing the charge and discharge profile, asdescribed in other embodiments. For this cell, the manufacturer'sprescribed charge profile is to use CC-CV at 0.5 C to 4.2 V. However,the fastest charge to any capacity is obtained by a direct constantvoltage charge at 4.2 V, with a limiting current set to the maximumrated 14.8 A.

Example 5 Stacked Actuator from High Density Electrodes

LiCoO₂-based and graphite-based electrodes of conventional designtypical of those used in the lithium ion battery field were used to forma bi-layer stacked actuator, shown in FIG. 16. This actuator differsfrom those in preceding examples which have used commercially availablecells in that the electrode formulation has been selected according tomethods well-known to those skilled in the art to provide a higherpacking density and a higher stiffness. Accordingly, the completedactuator exhibits higher stiffness and lower viscoelastic relaxationthan in the preceding examples. In addition, the negative electrode usesa platelet graphite which during processing takes on a preferredcrystallographic texture with the c-axis preferentially aligned in thedesired actuation direction. Consequently, the strains obtained aregreater than in the commercially available cells, and may be greaterthan expected for the LiCoO₂-graphite system under the conditions wherethe graphite is not preferentially aligned.

The electrodes were prepared by coating a formulation incorporating apowder of the respective active material, a polymer binder, and aconductive carbon additive, dispersed in an organic solvent. The LiCoO₂coating (510) was applied to one side of an aluminum foil currentcollector (570) while the graphite coating (530) was applied to one sideof a copper foil current collector (560). After drying and pressing, acell was assembled as shown in FIG. 16. A conventional polymer separator(520) was used, and a conventional organic carbonate electrolyte (LP30)(550) was used.

FIGS. 17 and 18 show the charge-discharge voltage curves and thecorresponding strain measured in this cell, measured under 1 MPa and 10MPa pre-stress respectively. Under 1 MPa pre-stress, FIG. 17, a strainof 3-4.3% was observed, corresponding to an actuation energy density of˜45 kJ/m3. Under 10 MPa prestress, FIG. 18, a strain of 2-3% wasobserved, corresponding to an actuation energy density of ˜300 kJ/m3.FIG. 19 shows results from another actuator of the same type, testedunder 10 MPa and 17 MPa uniaxial applies stress. In this instance, 2.3%and 1.8% strain, and 230 kJ/m³ and 300 kJ/m³ energy density, areobtained respectively at 10 and 17 MPa. It is further noted that under17 MPa, the rate of strain with capacity is the same as at the lowerpressures even though the total strain is less, which indicates that thefull capacity of the cell is not reached for kinetic reasons such as thecompression of porosity in the polymer separator, but that the activematerial has not substantially changed its actuation performance. It isunderstood that with improvements in design as described in otherembodiments, still higher strains and strain energy densities may beobtained from actuators using electrodes of this type.

The electrodes of this example were further coated on both sides oftheir respective current collector foils and assembled into a multilayerstacked actuator having a thickness of about 6 mm. These cells weretested under varying prestress levels, using a so-called CCCV profilesin which the voltage range was 3.0-4.2V, and a constant C/5 current wasapplied until the 4.2 charge voltage or 3.0 discharge voltage wasreached, at which point the voltage was held constant until the currentdecayed to less than C/50. A 10 minute rest at constant voltage and zerocurrent was also conducted between charge and discharge portions. FIGS.20 to 22 show the strain obtained under 1, 5 and 10 MPa stress, atcorresponding portions of the charge-discharge curve. Note that at 1MPa, a high strain of 4.1% is obtained. At 10 MPa, the strain is still2.5%, and the corresponding energy density is 249 kJ/m³. Here also, thecapacity of the cell decreases with increasing stress, showing that itis charge/discharge kinetics that are limiting the achieved strain andmechanical energy density and not the intrinsic capability of the activematerials used.

Example 7 Segmented Multi-element Electrochemical Actuator

Highly oriented pyrolytic graphite (HOPG), which is anear-single-crystal form of graphite, was used as the actuationmaterial. The direction of actuation was selected to be normal to thegraphene sheets, namely along the c-axis of graphite, as shown in FIG.23. Along this direction, the free strain of graphite is 10.4% and theYoung's modulus is 35 GPa. In order to have high mechanical loadingalong this direction while intercalating ions transverse to thisdirection, the HOPG was laser-machined into a square array of 25 squareposts, each of 0.2 mm×0.2 mm dimension at the top, and 0.4 mm height.Lithium was used as the ion intercalant. A conventional LiCoO₂ compositeelectrode on aluminum foil current collector was assembled proximally tothe HOPG posts as shown in FIG. 23. The two electrodes were separated byan insulating polymer separator film, and packaged in polymer sheet asshown for the actuator in FIG. 16.

FIG. 24 shows the actuation strain of this actuator under 100 MPapre-stress. While only partial lithiation of the graphite was achieved,the resulting strain was ˜1%, yielding an actuation energy density of˜1000 kJ/m3. This is more than 10 times the typical actuation energydensity of a PZT piezoelectric actuator.

In another actuator of this type, an array of small posts was carvedfrom a piece of HOPG, which was 1 cm square and 1 mm thick, by lasermicromachining. The dimensions of the posts were 0.2 mm square at thetop and 0.7 mm square at the bottom, and the height was 0.4 mm. Thesurface of the substrate part and that at the top of the posts wereparallel to the graphite layers. A SEM image of the sample is shown inFIG. 25.

A three layer assembly of copper foil, polypropylene membrane andanother copper foil was attached on the substrate, surrounding the HOPGposts. The lower copper foil was attached on the surface of thesubstrate part. Lithium foil was put on the upper copper foil and usedas a counter electrode. The polypropylene membrane insulated the twocopper foils. FIG. 25 schematically shows the cross-section of thesample. The sample was sealed in a bag of aluminum-laminate film filledwith liquid electrolyte. The electrolyte used was 1.33 M LiPF₆ dissolvedin a mixed solvent of ethylene carbonate, propylene carbonate, dimethylcarbonate, and ethyl methyl carbonate (4:1:3:2 by volume). The samplewas measured in a strain apparatus in which various preloads could beapplied along the normal to the surface. The sample was cyclicallycharged and discharged, and the change in thickness was simultaneouslymeasured by a precision displacement transducer equipped on theapparatus.

FIG. 26 shows strain and voltage as functions of time during acharge-discharge cycle by a constant current of 0.4 mA under amechanical preload of 100 MPa. The sample was first discharged untilvoltage became less than 0.01 V, then it was charged until voltagebecame more than 2 V. The curves clearly show that the strain wasinduced by the charge and discharge. The linear strain is 1.2% duringthe discharge, and this corresponds to a mechanical energy density of1,200 kJ/m³.

In another sample of this type, a layer of HOPG was bonded to an aluminaplate. A piece of HOPG, which was 5 mm square and 0.4 mm thick, wasfirst bonded to an alumina substrate, which was 12 mm square and 0.6 mmthick, with 25 μm thick copper foil at 650° C. for 1 hour in vacuumunder a stress of 50 MPa. The HOPG piece was bonded so that the graphitelayers were parallel to the surface of the substrate. An array of smallposts was carved from the HOPG part by laser micromachining. Thedimensions of the posts were 0.2 mm square at the top and 0.35 mm squareat the bottom, and the height was 0.4 mm.

A triple layer of copper foil, polypropylene membrane and another copperfoil was attached on the substrate, surrounding the HOPG posts. Thelower copper foil was attached to the copper layer that was used to bondthe HOPG part. Lithium foil was put on the upper copper foil and used asa counter electrode. The polypropylene membrane insulated the two copperfoils. The sample was sealed in a bag of aluminum-laminate film filledwith liquid electrolyte. The electrolyte used was 1.33 M LiPF₆ dissolvedin a mixed solvent of ethylene carbonate, propylene carbonate, dimethylcarbonate, and ethyl methyl carbonate (4:1:3:2 by volume). The samplewas measured in a strain apparatus in which various preloads could beapplied along the normal to the surface. The sample was cyclicallycharged and discharged, and the change in thickness was simultaneouslymeasured by a precision displacement transducer equipped on theapparatus.

FIG. 26B shows strain and voltage as functions of time during acharge-discharge cycle under a preload of 30 MPa. The sample wasdischarge at a current of 0.05 mA until voltage became 0.01 V, followedby additional discharge at a voltage of 0.01 V until the current decayedto less than 0.005 mA. Then, it was charged at a current of 0.05 mAuntil the voltage became more than 1 V, followed by additional charge at1 V until the current decayed to less than 0.005 mA. The linear strainis 4.3% during and mechanical energy density is 1,290 kJ/m³.

It is understood that with engineering improvements well-understood tothose skilled in the art of electrochemical materials and devices,greater intercalation and greater corresponding strain is achievable.For example, the width of the posts may be narrowed in order to increasethe extent of lithiation under a given current rate. At completelithiation giving ˜10% linear expansion, the actuation energy densityunder 100 MPa pre-stress is 10,000 kJ/m³.

It is also understood that many segmentation patterns may be applied tothis basic actuator design to improve load-bearing and intercalation.FIG. 27 shows one alternative design in which the posts are more widelyspaced so as to distribute the load over a larger macroscopic area, inwhich instance the lithiation source may be placed between theload-bearing posts.

Example 8 Large Stroke Electrochemical Lever Actuator

Large stroke electrochemical lever actuators may be prepared, andrepresent additional embodiments of the invention. A lever and fulcrummechanism are used to amplify the induced strain of multilayerelectrochemical actuators, hereafter referred to as the “activeelements” to distinguish from the actuator, which comprises these aswell as a mechanical assembly and optionally other sensors and controlsfor controlling the performance of the actuator. This actuator benefitsfrom a simple amplification mechanism, easy method of applying prestressat the actuator output, and an ideal and compact form factor for placingthe actuator in small spaces, exemplified by, but not limited to, suchapplications as actuating a rotor blade spar for trailing edge or rotorblade twisting actuation, deploying flaps in aircraft, watercraft, andland vehicles, deforming a mirror in an adaptive optical device,deploying solar panels in a satellite, latching or unlatching a door orlid, or opening and closing a valve.

Measurements of displacement under preload, actuation force, and devicestiffness have been conducted on the ELA. The results show thatactuators based on this approach are capable of performing significantmechanical work. The mechanical performance of the electrochemical leveractuator (ELA) was characterized using different kinds of activeelements. The results show that electrochemical actuators based on solidstate active compounds should be attractive for applications where highstrain, high energy density and high actuation authority are desirable.

The design of the ELA is shown schematically in FIG. 28 a, and withdimensional details in FIGS. 28 b and 28 c. While an actuator of similardesign in which piezoceramics are used as the active materials isavailable commercially for micropositioning applications (PhysikInstrumente, there are, in some embodiments, functional advantages inusing electrochemical actuation elements in an actuator of this type,including but not limited to the ability to generate much larger stroke.Referring to FIG. 28 a, the amplification ratio, given by the ratio ofthe displacement at the actuator output relative to the displacement ofthe active elements (here a stack of individual elements), is given byb/(a/2). The actuator of the example was designed to have anamplification ratio of six.

A stiffness analysis illustrates advantages of the present actuatorcompared to comparable piezo-powered devices. As shown by E. F. Prechtland S. R. Hall (Design of a high efficieny, large strokeelectromechanical acuator, MIT, Cambridge, Mass. 1998), to obtain thehighest coupling efficiency the stiffness of the expansive element, inthis case the active elements, should be much lower than the stiffnessof the coupler, in this case the elastic flexure. This is readilyaccomplished in the present case since, as shown in preceding examples,electrochemical actuators can be fabricated with stiffness much lowerthan that of many structural metals, ceramics, and composites. Inaddition, in order to reduce performance losses due to bending in thelever arm, the bending moment in the flexure should be low compared tothe bending moment in the lever arm. These considerations led to thedesign shown in FIG. 27.

Although the flexure can in principle be fabricated from numerousmaterials, in this example the frame was constructed of stainless steelwith a Young's modulus of E=170 GPa. This frame, having outer dimensions130 mm×32 mm×50 mm, transmits the load from the actuation elements tothe actuator output. A cavity of dimensions of 80 mm×20 mm×40 mm wasmachined in the frame to accommodate the actuation elements. The flexurehaving the dimensions in FIG. 27 was then realized by making a series ofprecision wire-EDM (Electric Discharge Machining) cuts (Model:ROBOFIL240 CC from Charmilles Technologies SA).

End caps were made of the same stainless steel as the support frame.They have a spherical surface with a radius of 20 mm and a thickness of15 mm for one endcap and 10 mm for the other. The radius of the end capscan also be increased to reduce Hertzian losses at the contacts. Shimswere also made of stainless steel in thicknesses from 0.1 mm to 0.8 mmand were used to fulfil the preload methodology of the ELA.

A preload is applied easily at the actuator output, see FIG. 27. Acompressive preload is necessary to eliminate mechanical backlash, andto maximize the actuator force and stroke output. When theelectrochemical active elements exhibit creep strain under load, shimscan be used between the end caps and the actuator element stack toensure that the creep strain is taken up under compressive preload.

A multitude of tests were conducted to characterize the performance ofthe ELA, using actuator elements of prismatic form factor similar tothose discussed in preceding examples. Displacement tests were carriedout with different compressive preloads. The preload was applied with anInstron apparatus (Model 5550 and Bluehill control software) at a loadrate of 460 N/h for most tests. After a desired peak preload value wasreached, a rest period was used to allow for creep deformation of theactive elements. The active elements were connected in parallel andsimultaneously charged and discharged for multiple cycles at variousrates, using the CCCV protocol. The amplified displacement at theactuator output was measured by the Instron crosshead, using a test rodwith a spherical surface of 5 mm diameter made of tungsten was used totransmit the induced displacement and load from the actuator output tothe strain gage and the load cell of the Instron crosshead.

FIG. 29 shows the output strain measured under a load of 270N, whichresults in a stress of 4 MPa on the active elements. The output averagedisplacement during charging is 3.42 mm, and for discharging is 3.72 mm,approximately an order of magnitude greater than can be expected from alever actuator using piezoceramic elements. With these values and theamplification factor we calculate a battery stack strain of approx.1.5%, which is consistent with the strains shown in preceding examplesfor these active elements under a few MPa stress. This implies a muchhigher stiffness for the frame than for the active elements, as isdesired, and a high mechanical efficiency for the device.

Example 9 Electrochemical Woven Actuator

An Electrochemical Woven Actuator (EWA) was designed, as part of thisinvention, whose properties allow for very large stroke and high forceactuation. While the embodiment described herein, for this actuator wasdeveloped for operation in a helicopter rotor blade, it is also suitablefor other engineering applications requiring large stroke actuation.

One of the main challenges in developing a novel actuator with theintercalation compounds was that the induced strain of the compounds hasan actuation direction not identical to the direction required for manyengineering applications. Considering this limitation, the developmentof actuation mechanisms that transform the principal strain direction ofthe active element (i.e., a multilayer electrochemical actuator) intothe appropriate direction required for the application was sought. Onedesirable aspect of the actuator sought was to enclose the activeelements with a layer of woven fibers, and to generate the strain andforce of the actuator in the horizontal direction by extending theactive element vertically. FIG. 30 shows the schematic view of theactuator, where three active elements (1) are enclosed by twoalternating fibers (2). On the top and bottom surfaces of each activeelement, a cap with a constant curvature (3) is attached to provide auniform normal stress. Clearly, a vertical extension of the activeelement reduces horizontal displacement of the actuator, and therefore,a contraction force is generated in the horizontal direction.

We constructed a first prototype EWA by using stainless steel wires asthe weaving material, and tested its performance to validate itsconcept. The active elements comprised three commercial batteries, eachone of them with its caps machined from aluminum and attached with epoxyglue. The geometry of the EWA was chosen to maximize the energyefficiency of the device, while the resulting thickness of the EWA isacceptable. In order to test the performance of the EWA, it wassubjected to a constant load while the batteries were charged, as shownin FIG. 31(a). The actuator strain was measured and compared with thestrain in one of the batteries. The measurements showed a smaller strainthan expected, due to some creep which was produced in large part by thecommercial lithium ion cells used as active elements. If, however, thecreep is removed from the data, a strain very close to the predictedvalue is obtained. FIG. 31(b) shows the graph obtained from the test,with the creep portion removed.

FIG. 31 provided predicted values, and in FIG. 32 the expected stiffnessand strain bounds were plotted against the ratio of the actuator lengthL and the battery length w, which demonstrated good correspondence.

Example 10 Actuated Beams

It was also of interest to construct an actuated beam, as shown in FIG.33. One face of the beam was mechanically constrained by two layers of afiberglass weave. 27 actuators were arrayed as shown in FIG. 33, andepoxy resin was poured as the matrix for the beam. The 27 actuators wereelectrically joined in parallel, and a power source was used to chargeand discharge them within the voltage limits specified by themanufacturer (ATL Corporation). The beam was tested by clamping one endand using a laser beam as a “light lever” to measure the deflection ofthe other end. Upon charging and discharging, the tip of the beamdeformed by 1 mm. This corresponds to a surface strain of 400microstrain. Thus it is demonstrated that the electrochemical actuatorsof the invention can be used to provide mechanical actuation in a beamstructure.

Example 11 Electrochemically Based Fluidics Actuator

While electrochemical pumping of a gas with a solid electrolyte has beenused in prior art to perform actuation, a high stress is not possible,due to the compressibility of the gas. Since liquids have much lesscompressibility than gases their utilization produces greater actuationauthority.

In this concept an electrolytic membrane, which pumps an ion from oneside of a device to another, generating a liquid rather than a gas inthe process, is used. By pumping a liquid, much higher actuation forcescan be produced since liquids have much lower compressibility. Actuatorsof this kind can be used in fluidic and micro fluidic devices, microhydraulic devices, nastic structures compressing cellular micro-fluidicor micro hydraulic devices, and others.

A proton-conducting membrane may be utilized to transport hydrogen ionsto produce water, resulting in a net volume expansion (FIG. 34). Uponcharging, for each mole of H+ transported across the membrane, producingone mole of water, from one half mole of OH, there is a net volumechange: $\begin{matrix}{{{For}\quad H_{2}O} = {\frac{18.02\quad g\text{/}{mole}}{1.00\quad g\text{/}{cm}^{3}} = {18.02\quad{cm}^{3}\text{/}{mole}\quad H_{2}O}}} \\{{{For}\quad H_{2}O_{2}} = {\frac{34.01\quad g\text{/}{mole}}{1.4067\quad g\text{/}{cm}^{3}} = {24.18\quad{cm}^{3}\text{/}{mole}\quad H_{2}O_{2}}}} \\{= {12.09\quad{cm}^{3}\text{/}{mole}\quad{HO}}}\end{matrix}$

Thus the volume expansion is:${\frac{18.02 - 12.09}{12.09\quad g\text{/}{cm}^{3}} \times 100} = {49.05\quad\%}$

1. An electrochemical actuator, comprising: a. a negative electrode; b.a positive electrode; and c. an intercalating species; wherein saidelectrochemical actuator is subjected to an applied voltage or current;whereby application of said voltage or current or cessation thereofinduces intercalation of said species in electrodes of said actuator,resulting in a volumetric or dimensional change of said actuator andlinear strain is produced, ranging from 1-300%.
 2. The electrochemicalactuator of claim 1, wherein said volumetric or dimensional change is insaid negative electrode or said positive electrode or a combinationthereof.
 3. The electrochemical actuator of claim 1, wherein saidvolumetric or dimensional change ranges from 0.1-300%.
 4. (canceled) 5.The electrochemical actuator of claim 1, wherein said negative electrodeor positive electrode undergoes a phase change, anisotropic expansion oranisotropic contraction upon intercalation.
 6. The electrochemicalactuator of claim 1, wherein said negative electrode serves as a donoror acceptor or combination thereof, of said intercalating species. 7.The electrochemical actuator of claim 1, wherein said positive electrodeserves as a donor or acceptor or combination thereof, of saidintercalating species.
 8. The electrochemical actuator of claim 1,wherein said negative electrode may serve as a source for saidintercalating species.
 9. The electrochemical actuator of claim 1,wherein said positive electrode may serve as a source for saidintercalating species.
 10. The electrochemical actuator of claim 1,wherein said negative or positive electrode, or combination thereofcomprises a high elastic modulus compound.
 11. The electrochemicalactuator of claim 10, wherein said compound exhibits an elastic modulusranging between 10-500 GPa.
 12. The electrochemical actuator of claim11, wherein said compound exhibits an elastic modulus ranging between50-150 GPa.
 13. The electrochemical actuator of claim 1, wherein saidnegative electrode, positive electrode, or combination thereof comprisesan ion transition metal oxide.
 14. The electrochemical actuator of claim13, wherein the ion in said ion transition metal oxide is a proton or analkali metal or an alkaline earth metal.
 15. The electrochemicalactuator of claim 14, wherein the alkali metal is lithium.
 16. Theelectrochemical actuator of claim 1, wherein said negative electrode,positive electrode, or combination thereof comprises: LiCoO₂, LiFePO₄,LiNiO₂, LiMn₂O₄, LiMnO₂, LiMnPO₄, Li₄Ti₅O₁₂, TiSi₂, MoSi₂, WSi₂ ormodified compositions or solid solutions thereof.
 17. Theelectrochemical actuator of claim 1, wherein said negative electrode,positive electrode, or combination thereof comprises titanium oxide,vanadium oxide, tin oxide, antimony oxide, cobalt oxide, nickel oxide,iron oxide, or a combination thereof.
 18. The electrochemical actuatorof claim 1, wherein said negative electrode, positive electrode, orcombination thereof comprises a metal or intermetallic compound.
 19. Theelectrochemical actuator of claim 1, wherein said negative electrode,positive electrode, or combination thereof is lithium or a lithium-metalalloy, which may be crystalline, nanocrystalline, or amorphous.
 20. Theelectrochemical actuator of claim 1, wherein said negative electrode,positive electrode, or combination thereof comprises aluminum, silver,gold, boron, bismuth, gallium, germanium, indium, lead, antimony,silicon, tin, or a combination thereof.
 21. The electrochemical actuatorof claim 1, wherein an electrode comprises carbon in the form ofgraphite, a carbon fiber structure, a glassy carbon structure, a highlyoriented pyrolytic graphite, a disordered carbon structure or acombination thereof.
 22. The electrochemical actuator of claim 1,wherein the intercalating species is an ion.
 23. The electrochemicalactuator of claim 1, wherein the intercalating species is a proton or analkali metal or an alkaline earth metal.
 24. The electrochemicalactuator of claim 1, wherein said negative electrode, positiveelectrode, or combination thereof comprises a porous aggregate ofparticles. 25-27. (canceled)
 28. The electrochemical actuator of claim1, wherein said voltage is 0.1-15V.
 29. (canceled)
 30. Theelectrochemical actuator of claim 1, further comprising an electricallyconductive current collector, a separator, or a combination thereof. 31.The electrochemical actuator of claim 30, wherein said separator isporous or rigid.
 32. The electrochemical actuator of claim 31, whereinsaid porous separator comprises a microporous polymer or a porouselectronically insulating ceramic material.
 33. The electrochemicalactuator of claim 31, wherein said porous separator comprises amultiplicity of insulating polymer or ceramic particles.
 34. Theelectrochemical actuator of claim 33, wherein said porous electronicallyinsulating ceramic material comprises alumina, an aluminosilicate,cordierite, a silicate glass, or electronically insulating mixed-metaloxides, nitrides or carbides.
 35. The electrochemical actuator of claim1, the electrodes of which further comprise a conductive additive. 36.The electrochemical actuator of claim 1, further comprising anelectrolyte.
 37. The electrochemical actuator of claim 36, wherein saidelectrolyte is a solid or liquid electrolyte.
 38. The electrochemicalactuator of claim 1, further comprising an external packaging layer. 39.The electrochemical actuator of claim 38, wherein said externalpackaging layer is an electrochemically-insulating layer, a protectivelayer or a combination thereof.
 40. The electrochemical actuator ofclaim 1, wherein said actuator has a blocked stress of between 1-1000MPa.
 41. An apparatus comprising at least one electrochemical actuatorof claim
 1. 42. The apparatus of claim 41, wherein said apparatus isadaptive.
 43. The apparatus of claim 42, wherein said actuator is usedas an element to apply stress at a site on said apparatus distal to saidactuator.
 44. The apparatus of claim 41, wherein said apparatusamplifies said volumetric or dimensional change induced by saidactuator.
 45. The apparatus of claim 41, wherein said apparatus is inthe form of a woven structure comprising said at least oneelectrochemical actuator.
 46. The apparatus of claim 45, wherein saidactuator amplifies stress in said woven structure.
 47. The apparatus ofclaim 45, wherein said apparatus is in the form of a lever and fulcrummechanism, and said lever comprises said at least one electrochemicalactuator.
 48. The apparatus of claim 47, wherein said actuator amplifiesstrain in said apparatus.
 49. A Multilayer Stacked ElectrochemicalActuator, comprising: a. two or more negative electrode layers; b. twoor more positive electrode layers; and c. an intercalating species;wherein said Multilayer Stacked Electrochemical Actuator is subjected toan applied voltage or current; whereby application of said voltage orcurrent or cessation thereof induces intercalation of said species inelectrodes of said actuator, resulting in a volumetric or dimensionalchange of said actuator and linear strain is produced, ranging from0.5—5%.
 50. The Multilayer Stacked Electrochemical Actuator of claim 49,wherein intercalation of said species, in said electrodes, results in avolumetric or dimensional change of said actuator.
 51. The MultilayerStacked Electrochemical Actuator of claim 49, wherein said volumetric ordimensional change ranges from 0.1-300%.
 52. The Multilayer StackedElectrochemical Actuator of claim 49, wherein said negative electrode orpositive electrode undergoes a phase change, anisotropic expansion oranisotropic contraction upon intercalation.
 53. The Multilayer StackedElectrochemical. Actuator of claim 49, wherein said negative electrodeserves as a donor or acceptor or combination thereof, of saidintercalating species.
 54. The Multilayer Stacked ElectrochemicalActuator of claim 49, wherein said positive electrode serves as a donoror acceptor or combination thereof of said intercalating species. 55.The Multilayer Stacked Electrochemical Actuator of claim 49, whereinsaid negative electrode may serve as a source for said intercalatingspecies.
 56. The Multilayer Stacked Electrochemical Actuator of claim49, wherein said positive electrode may serve as a source for saidintercalating species.
 57. The Multilayer Stacked ElectrochemicalActuator of claim 49, wherein said positive electrode, said negativeelectrode, or a combination thereof comprises a metal or intermetalliccompound.
 58. The Multilayer Stacked Electrochemical Actuator of claim49, wherein said positive electrode, said negative electrode, or acombination thereof comprises lithium or a lithium-metal alloy.
 59. TheMultilayer Stacked Electrochemical Actuator of claim 49, wherein saidpositive electrode, said negative electrode, or a combination thereofcomprises carbon, aluminum, silver, gold, boron, bismuth, gallium,germanium, indium, lead, antimony, silicon, tin, or a combinationthereof.
 60. The Multilayer Stacked Electrochemical Actuator of claim59, wherein said carbon is graphite, a carbon fiber structure, a glassycarbon structure, a highly oriented pyrolytic graphite, a disorderedcarbon structure or a combination thereof.
 61. The Multilayer StackedElectrochemical Actuator of claim 49, wherein said positive electrode,said negative electrode, or a combination thereof comprises lithiumtitanium oxide, titanium oxide, vanadium oxide, tin oxide, antimonyoxide, cobalt oxide, nickel oxide, iron oxide, or a combination thereof.62. The Multilayer Stacked Electrochemical Actuator of claim 49, whereinsaid positive electrode, said negative electrode, or a combinationthereof comprises an ion transition metal oxide.
 63. The MultilayerStacked Electrochemical Actuator of claim 62, wherein said ion of saidion transition metal oxide is a proton or an alkali metal or an alkalineearth metal.
 64. The Multilayer Stacked Electrochemical Actuator ofclaim 63, wherein said alkali metal is lithium.
 65. The MultilayerStacked Electrochemical Actuator of claim 49, wherein said positiveelectrode, said negative electrode, or a combination thereof comprisesLiCoO2, LiFePO4, LiNiO2, LiMn2O4, LiMnPO4, Li₄Ti₅O₁₂, or modifiedcompositions or solid solutions thereof,
 66. The Multilayer StackedElectrochemical Actuator of claim 49, wherein said negative electrode,positive electrode, or combination thereof comprises a porous aggregateof particles of said electrode material.
 67. The Multilayer StackedElectrochemical Actuator of claim 66, wherein said porous aggregate issintered.
 68. The Miltilayer Stacked Electrochemical Actuator of claim67, wherein said porous sintered aggregate is a composite, furthercomprising a conductive additive or sintering aid.
 69. The MultilayerStacked Electrochemical Actuator of claim 66, wherein said aggregatecomprises crystallites of a compound sharing a common orientation ortexture of their crystal axes.
 70. The Multilayer StackedElectrochemical Actuator of claim 49, wherein said intercalating speciesis an ion.
 71. The Multilayer Stacked Electrochemical Actuator of claim70, wherein said ion is a proton or an alkali metal or an alkaline earthmetal.
 72. The Multilayer Stacked Electrochemical Actuator of claim 107,wherein said alkali metal is lithium.
 73. The Multilayer StackedElectrochemical Actuator of claim 49, wherein said structural change isa result of intercalation of said species in said negative electrode orsaid positive electrode or a combination thereof.
 74. The MultilayerStacked Electrochemical Actuator of claim 49, wherein said voltage is0.1-15V.
 75. The Multilayer Stacked Electrochemical Actuator of claim49, further comprising a current collector, a separator or a combinationthereof.
 76. The Multilayer Stacked Electrochemical Actuator of claim75, wherein said current collector comprises a conductive material. 77.The Multilayer Stacked Electrochemical Actuator of claim 75, whereinsaid separator is porous or rigid.
 78. The Multilayer StackedElectrochemical Actuator of claim 77, wherein said porous separatorcomprises a microporous polymer or a porous electronically insulatingceramic material.
 79. The Multilayer Stacked Electrochemical Actuator ofclaim 77, wherein said porous separator comprises a multiplicity ofparticles of said polymer or ceamic material.
 80. The Multilayer StackedElectrochemical Actuator of claim 79, wherein said porous electronicallyinsulating ceramic material is alumina, an aluminosilicate, cordierite,a silicate glass, or electronically insulating mixed-metal oxides,nitrides or carbides.
 81. The Multilayer Stacked ElectrochemicalActuator of claim 49, the electrodes of which further comprise aconductive additive.
 82. The Multilayer Stacked Electrochemical Actuatorof claim 49, further comprising an electrolyte.
 83. The MultilayerStacked Electrochemical Actuator of claim 82, wherein said electrolyteis a solid or liquid electrolyte.
 84. The Multilayer StackedElectrochemical Actuator of claim 49, further comprising an externalpackaging layer, which is an electrochemically-insulating layer, aprotective layer or a combination thereof.
 85. The Multilayer StackedElectrochemical Actuator of claim 49, wherein said actuator is subjectedto a uniaxial or hydrostatic pressure ranging from 10,000-45,000 psi,(69-310 MPa).
 86. The electrochemical actuator of claim 1, wherein saidactuator is a Rotational Electrochemical Actuator, comprising rolledlayers of: a. said negative electrode; b. said positive electrode; andc. said intercalating species wherein said rolled layers assume alaminate configuration, wherein when said Rotational ElectrochemicalActuator is subjected to an applied voltage or current, said rolledlaminate configuration winds or unwinds, and torque is produced.
 87. TheRotational Electrochemical Actuator of claim 86, wherein when saidrolled laminate configuration winds or unwinds, rotary motion isproduced. 88-127. (canceled)
 128. The electrochemical actuator of claim1, wherein said actuator is a Continuous Fiber Electrochemical Actuator,wherein said negative electrode is a fibrous electrode and said positiveelectrode is a counter electrode, whereby said volumetric or dimensionalchange of said actuator results in said fibrous electrode undergoingelongation or contraction.
 129. The Actuator of claim 128, wherein saidfibrous electrode comprises at least one fibrous layer. 130-172.(canceled)
 173. A method of actuation, comprising the step of applying avoltage or current to an actuator comprising a negative electrode, apositive electrode and an intercalating species, wherein applying saidvoltage or current induces intercalation of said species in saidactuator, whereby said intercalation induces a volumetric or dimensionalchange of said actuator and linear strain is produced; ranging from1-300%.
 174. The method of claim 173, wherein said voltage or currentare varied as a function of time. 175-212. (canceled)
 213. A nasticstructure comprising at least one electrochemical actuator, comprisingan negative electrode, a positive electrode, and an intercalatingspecies, wherein following application of a voltage causing current flowin said actuator, intercalation of said species produces a change involume in said actuator, such that a bend or other deformity is inducedin said nastic structure. 214-215. (canceled)